The Curia Powers are a fun and useful part of playing as a Catholic nation, and it's worthwhile to try and have as many of them active as possible. The actual experience of keeping them active, however, is somewhat frustrating, because there's no indication when they expire, so you have to check the papacy interface periodically to make sure you still have them all active. I can see two ways to alleviate this irritating micro:
The simple approach is to provide a notification of some sort when a curia power has or is about to expire. This would eliminate the need to periodically check the interface, but it's still rather fiddly.
A more complex, but in my opinion superior, approach would be to emulate what Stellaris has done with edicts and make curia powers toggleable abilities that provide an indefinite ability for a cost of papal influence. This would be more work to implement, but would mean you can simply activate the curia powers you want to use and not worry about them any longer. (The powers that give stability and mercantilism wouldn't be changed in this idea, since they don't provide any ongoing effects.)
The simple approach is to provide a notification of some sort when a curia power has or is about to expire. This would eliminate the need to periodically check the interface, but it's still rather fiddly.
A more complex, but in my opinion superior, approach would be to emulate what Stellaris has done with edicts and make curia powers toggleable abilities that provide an indefinite ability for a cost of papal influence. This would be more work to implement, but would mean you can simply activate the curia powers you want to use and not worry about them any longer. (The powers that give stability and mercantilism wouldn't be changed in this idea, since they don't provide any ongoing effects.)