Seems like an interesting question... I am trying to find the answer and plan to illustrate it with news articles from that period. So if you are interested, check back in a couple of days when this post will be finished.

The question regarding the transition to Wyndham Garden can be answered quite precisely. CrestHil by Hilton Buffalo Grove opened on October 21, 1989. Like almost all 'brand' hotels in the world, it was a franchise hotel. This means that the owner of the building is someone else, not Hilton itself. And the operational management of the hotel is often carried out by another specialized party. Such a hotel management company often has multiple hotels in various cities under its care, and these can be franchises of one of the brands of Marriott, Hilton, IHG, Wyndham, Radisson, etc. A franchise contract typically has a duration of ten years (although with newly built luxury hotels it is often for 20-30 years) . A one-time franchise fee of, for example, $70,000 has to be paid. But it doesn't stop there; in addition, equipment and goods must be purchased from approved suppliers and training associated with the brand must be followed. However, the largest cost for the operator is the percentage of the room price (or the total folio of each sold room) that has to be paid.

I have made up the percentages below, but they are probably close to reality.

Per sold room per night this goes to Hilton:

• 5% - To be part of the CrestHil franchise.
• 3.5% - Marketing fee, to promote the brand.
• 1.5% - To use the reservation system.
• 5% - Only if the customer is a Hilton Honors member. It covers the Honors program and the points awarded to customers.
• ?% - Maybe some other percentages.

Now, I have done some research on the internet, and Hilton seems to have the highest fees and percentages of the four major brands, while Wyndham has the lowest. Over a ten year period, for a hotel of this size, it could make a difference of at least a million-dollars, in my calculations. So the fee structure can determine whether you switch labels after ten years or not. If your hotel is continuously sold out and many of the guests take part in the Hilton Honors program, and they pay a few percent more for their room each year, then there is little reason to switch. But if your average room prices do not rise and few guests arrive because of your 'Hilton' name, then it may be time to look for something new.

To renew a franchise agreement after ten years, it is necessary to make significant investments in your hotel. Essentially, most, if not all, furniture and equipment in the room, the carpets, and wallpaper must be replaced or renewed after ten years. This didn't really play a role at the hotel in the switch to Wyndham, I think, because between November 1999 and January 2000, $3 million was spent on the hotel. The general manager stated in this article from The Daily Herald that the reason was to upgrade to a full-service hotel, which was not possible with Hilton Garden Inn. I'm not sure if that's entirely correct. At that time, I visited a couple of newly built HGIs, and they all operated with a restaurant offering breakfast, lunch, and dinner, and limited room service until 10 pm. If they had stayed with Hilton, those same adjustments would have been necessary.

Newspaper articles often tell only half the truth. Something that I think must have played a role in the background: in 1998, rumors arose about a merger between Promus and Hilton. Promus from Memphis, Tennessee, was the owner of the remaining subsidiaries of the Holiday Inn Corp. The brand itself had already been sold to an English company (Bass PLC brewery) in 1989, which eventually became InterContinental Hotel Group. But at that time at the end of the century, Promus represented these brands:

• Hampton Inn (& Suites)
• Embassy Suites
• Homewood Suites
• DoubleTree (Club | Suites)

Although the Hilton/Promus merger only took place in December 1999, I think that in Buffalo Grove, they were afraid of losing Hilton customers to former Promus hotels in Chicagoland. Before the merger, there were 13 hotels affiliated with Hilton in and around Chicago, and after that, 44. (source: New guest in town https://www.newspapers.com/article/c...ago/160215664/). Meanwhile, Wyndham was a much more exclusive and better-rated hotel, with lower franchise fees. I suspect that a lack of loyal Hilton customers and the hope for higher room rates played a role in the decision to switch to Wyndham. The hotel had two private tennis courts, and the business park was next to the Buffalo Grove Golf Course, so it was more than an average business park / airport HGI hotel.

Another reason I could imagine... when CrestHil was announced in 1987, there was talk of ten hotels opening in the first year and possibly twenty five per year in the years after. But after the fourth hotel, development completely stalled. Due to the economic downturn, no one was interested in starting an HGI anymore. It wasn't until 1996 that the Hilton Garden Inn brand was revived. The first new Hilton Garden Inn opened its doors in 1997 in Irving, Texas. What I think is funny: when you take a look at that hotel on Google Maps, you can still see some remnants of those arched windows of CrestHil. Example: https://maps.app.goo.gl/2966NvGwv6UzYz2d8 . Haven't noticed that at any other HGI that opened after Irving Los Colinas, at best the arches became triangles.

As mentioned: the location in Irving only opened in 1997, but all that time, the operator at the Buffalo Grove hotel had been paying a marketing fee for every guest staying, for a hotel brand that just didn't expand as was promised. Why would you continue such a relationship? Wouldn't you rather be the ninth Wyndham Garden in the Chicago area and be part of a success story? (Though this kind of contradicts with what I thought about Hilton growing from 13 to 44 hotels.)

I haven't found anything at all about the switch to Four Points by Sheraton. Using Google Streetview, it is obvious that it happened sometime between 2015 and 2017. And like what was written in the question: the oldest Four Points review on Tripadvisor goes back to December 2016. Couldn't find anything about the conversion on any other booking or review site, or in other news media.

I did find a story indicating that the first CrestHil was originally planned to be built in Camarillo, CA: https://www.newspapers.com/article/c...hil/160296498/ but it never materialized. According to the LA Times edition of December 20, 1987, (Mini-Hilton Hotel With 156 Rooms Set for Camarillo - Los Angeles Times) the hotel was supposed to be located at Las Posas Road and Daily Drive. The site is likely where a Hampton Inn & Suites opened in 2004. The plot which also hosts a Carl's Jr, Pollo Loco and McDonald's, would have been suitable for a CrestHil by Hilton. On the opposite site of the road is a Days Inn, built in 1970. The Las Posas Plaza mall, including a Ralph's, was already present in 1987, ruling out those locations. (Check Google Maps.)