PlayStation Advent Calendar Credits?

For the PlayStation Advent Calendar you have to buy lots with your credits.

Does anyone know whether these credits are only valid for the advent calendar or whether you can buy other things with them later?

In my opinion, this advent calendar is not worth it in retrospect, as you have to be very lucky. I once spent 100,000 credits on the Ps5 there and didn't win. The credits are only for tickets.