Similar worries have been raised in this forum for like a hundred times, so it might be of the most concern of Tinto. Anyway, PDS games (CK3, v3 and EUIV) can not actually find a way do deal with this in a compete sense. HOI4 players can play until the end of WWII, but for players, it often happens in around 1941 or 1942...
I saw a saying in this forum, spoken by Johan or quoted from Sid Meier - which I forget - saying that players can not accept failure because it would be considered as the fault of the players themselves. While the players play the game to gain happiness and enjoyment, it's indeed something hurt.
Studio Red (I'm not sure if it is red. I mean the one in charge of CK3) is exploring something special on this, by allowing players to switch to others playable character in their house. That's quite a revolutionary approach I supposed - a fundamental revolution against the traditional PDS gameplay - but suits CK3 only.
Johan presented his concern about the difficulty on creating and maintaing other bookmarks / start date. It's reasonable since PjCsr's pops and locations are too many, but taking experience from CK3 - it's kinda a good way to solve this.
The problem is, that once there would be more bookmarks or start dates, there have to be at least four or five one at last - considering that PjCsr covers a history about 500 yrs. CK3 is working on their 3rd start date now, but, speaking of their Struggle mechanic, they have to balance and adjust Iberian Struggle for every start date they made, let alone that there would be more start dates in the future.
Anyway, we may expect some mods about more start dates soon after the releasing of PjCsr.