I cannot comment on GrapheneOS extending the longevity of my phone (I just haven't been running it long enough), but I did notice an increase in battery life.

I was running stock Android for 4 months after buying a 6a, and the battery life was pretty abysmal. Now, the battery lasts quite a bit longer and I feel like I have a phone that can actually be used longer in between charges.

As to your second point, yeah, I completely agree. It's not unlike my decision years ago to ditch Windows and run Linux exclusively. I found myself in a different ecosystem that took a bit of time to get really comfortable with, but the motivation for more privacy and control over my pc outweighed some of the initial hurdles I experienced. Eventually, I found myself more at home in this new environment - so much so that I wouldn't even think about reverting back to Windows.

In this day an age, any attempts to gain some sort of control over one's privacy and security is going to be met with certain challenges and sacrifices, but I think the eventual benefits will far outweigh any initial annoyances that usually come with any change in habit.