I think we can thank Hilton for the confusion.

But I will say that I think rollover is a good benefit, though as far as I can remember it has not been of any benefit to me. I have qualified for Diamond based on actual nights stayed during the year as far as I know all the way back to the end of the rolling tier era. (Now that was confusing, but fun to manipulate. )

This could be the first year that rollover helps me as I rolled over 60 nights (thus already Diamond qualified) and only have 15 nights to date. At this time I do expect to clear the 30 night threshold unless the pandemic returns in force. But I don't expect much of a rollover for me this year, certainly nothing close to 60 nights.

Cheers!
David