... since you haven't selected them yet, you could just pick another benefit if you're not going to use the GUCs.
... If you're low on miles but earn and burn a lot then I'd think more about waiting.
That was part of my thought process ... unsure whether i'll have any additional int'l travel next year, in which case a different benefit would be a better value.
I'm sort of earn-and-burn ... my spend with DL is typically ~30k/yr *9 for PM = 270K/yr. I typically do one international trip per year and take Mrs. pauly_long with me. She flies in J on miles (R/T available for 140K RDM right now) and then I upgrade myself on the ticket work bought (120K RDM) and then it takes me another year to build the balance back up.