I'd check them out in person if at all possible, even if that meant spending the first week of the 2-3 months in a few different places. I've stayed at a great Holiday Inn, and an absolutely dreadful one, ditto with several other brands mentioned, including Wyndham, Best Western and Embassy Suites. The buildings, as well as the staff can make or break a stay. For a long stay there should certainly be room for negotiation with the property manager about room type, location, rates, etc. For example, one I stayed in had a great manager, who kept the rooms either side of me, and above me empty if they could so I wouldn't be disturbed (it was the sort of place that families stayed, a million to a room as someone mentioned above, so this was a real benefit to me) At that property we also came to an arrangement on laundry (aka not the silly rates on the hotel laundry list). Having an in room washer / dryer can be a real plus, although it is not terribly common. Next best would be having the hotel have laundry service (not all do), and thirdly a laundry room guests can use. Otherwise you are going to have to find a dry cleaner or Laundromat somewhere, and that can be both time consuming and expensive (depending on what your employer covers).

I'd consider the following:

1. Room comfort - at minimum on business I want a comfy bed (for me that means firm), a decent sofa to sit at, and a table I can use as a dining table, and a proper work desk and chair. A decent TV (in a sensible place - so may are at weird angles), a great bathtub and shower and enough space for my belongings are also key. Decent heat / AC depending on where you are, and windows that open are also important. A quiet location, or very good insulated glass are also things you may want to look at.

2. Facilities in the hotel I need - I need somewhere to work out, ideally a swimming pool. I once spent a long time at one hotel that didn't so I got gym membership up the road which worked well. A restaurant of some sort (not a vending machine a la some HIX) and a bar so I can actually socialize if I want to. Having a kitchen may be very important to you - it depends on what and how your normally eat, and what is available locally (and your schedule).

3. Location - both to the work office, but also things to do in the evening (parks to walk in, restaurants, shops etc.) I don't want to be reliant in having to take a car everywhere.

4. Points / tier / airline mile potential - the various rules on extended stays could mean that you are better staying at your property Sun - Sat and spending Saturday night elsewhere (so it becomes multiple 'stays' not one block). This varies by chain and by individual hotel. Also check with your employer - depending on the work pattern, would they be ok with you staying somewhere else Friday and Saturday night (aka a weekend somewhere else) if it is a comparable cost? Could be a good way to maintain your sanity, and see a bit more of your destination state / country.