The bell-shaped clematis are still blooming long after my others have stopped
Is this typical? Do bell-shaped ones have a longer bloom time ?

From personal experience with my Rooguchi, I think you may be right, I still have a smattering of blooms on it right now and it's been blooming since spring.

I only planted them last spring (2019) and did not know if this was just the exuberance of youth or an expectation. I guess time will tell for sure
they are lovely and I am enjoying their garden presence