In this example, the 10 elite rollover nights from 2018 must be used in 2019 and can not be applied to the 2020 calendar year. (hiltonhonors3.hilton.com)
I think the loss of rollover nights is a bigger issue than a number of people seem to think it is (based on what I've read elsewhere). (travelingformiles.com)
Of all these changes, the elite rollover nights seem to offer the most potential value. (travelcodex.com)