Didnt look too much into it but my gut feeling based on the price says its too cheap to be able to keep the lights on for centuries.

I would rather do a one time payment because they sure wont get money from me when i am dead. So a one time payment must basically be big enough to generate enough interest/stock market returns to make it worth their while too keep the lights on forever. I dont see this with a 50€ Subscription. Maybe they would do it like an ETF Investment Account which signs you up for Cyro Preservation after reaching a certain size. The money would have to be withdrawable while being alive though.