Does someone know if these have to be consumed in the calendar year in which they are earned or within some limited amount of time afterwards?

I'm unable to get a comp room for a few nights of an upcoming trip when signed in to Caesars Reward normally but I have plenty of blocks of 5000 TCs earned from play in calendar year 2021 if I can use a few of those instead.

I seem to remember though that these have to be used fairly quickly.