How does rollover work?
 

If I stay 150 nights this year, and 0 next year, that means I qualify for Diamond this year, roll over 90 to next year so I qualify and then roll over 30 to the following year?
Same scenario, but next year I stay 1 night, does that mean I'd roll over 31 nights to the following year?

Nights can only roll over into the following year. So you'd roll over 90 to next year, then 0 to the following year. The rollover begins once you've reached the official qualification threshold, so once you reach 60 nights next year, you'd then begin to accumulate rollover nights that would count towards the following year. At least that's how I understand it though it's somewhat unclear. Also does anyone know if there's somewhere to check the total number of nights that you're on track to have rolled over?

Its defined very clearly- roll over nights only apply for the following year not the year(s) after.

Here is the link with all the info...

https://hiltonhonors3.hilton.com/rs/...RolloverNights

I assume that if one qualifies for diamond on stays, but doesn't have enough actual nights to reach that requirement, then there is no rollover?

As I read the FAQs you are Correct. The FAQs state that a diamond needs 61 nights to begin to rollover.

How about spend rollover?

Spend Rollover only applies once you meet the minimum Digital Key Rollover Threshold. :)

So after 120 nights in one year, there is no benefit at all of staying more? I guess I'm at 130 now, so no point in giving Hilton more nights. In fact, I don't need to stay at all next year, and none will rollover until the following year, so I could just take a year off Hilton.

Too bad they didn't allow continuous rollover - if they did, I'd give them another ~30 nights this year.

I have never figured out this theory. Given this statement, I should never stay at a Hilton again given I am Lifetime Diamond.

Well, Hilton has never offered this benefit in the past. In fact, it has not even happened yet. I for one think this is a very valuable benefit. But I can't understand how you ever stayed at a Hilton even one night in the past, since this benefit didn't exist?

In the past, I would stay the min nights for Diamond, then go to Marriott as I worked toward their lifetime Platinum Status. Now I've hit that. So deciding what to do.

The benefit is that you stay in a hotel. Not sure what you are expecting.

Rollover only starts from the end of this year (rolling over into next year), so that's not what you had.

Most likely you received one of the targeted promos where stays counted both in "this year" (ie, 2017) and also "next year" (2018), and you had 7 such stays. Thus you started 2018 with 7 stays.