Yes with the smoothness (ie the resolution or number of available dutycycles) but not with the TIME it takes to fade the LED*
You can get a fairly high (certainly high enough to not notice any flickering) while maintaining full (10bit) resolution of the CCP module. Going below that point gives you nothing in terms of smoothness.
[*] Of course, if have a fixed delay of 10ms between duty cycles updates and then change the frequency enough to get from 8 to 10bits without changing the delay it WILL take longer to to do a full fade but THAT's pretty obvious.

/Henrik.