Any extra time, or " Fiddlin'" with a flintlock occurs in setting up the lock to fire properly. Once you have that done, I don't see much difference in how a flintlock is maintained and a percussion gun is maintained. There is a higher Learning Curve to shooting Flintlocks- I give you that. But, that is largely due to the fact that there are ONLY a few companies making Quality locks that don't require much, if any work on them by the shooter to get the lock to function properly.
Many other locks can be improved with just a little work, but you need to know what to do and how to do it. That is where the Education comes into play, and, frankly, most shooters don't want to be bothered. They will try a flintlock, but if they don't get the results they desire, they abandon the guns rather quickly, and move on to some other kind of gun.
When I joined my local BP Club, we had exactly 3 members who owned flintlocks, and None of them really knew anything about how to make them shoot. Each of the guns had locks with different problems.
Then, a new member joined, who was a BP Gunsmith and gun builder, who had only worked on FLINTLOCKS! I had to teach HIM how to tune Percussion locks. In return, he helped me understand the "mysteries" of flintlocks.
Once I understood how the parts worked, the only difference between flintlocks and percussion locks is that the flintlock has another spring- this one on the outside of the lock that keeps the Frizzen closed when the barrel is pointed to the ground. Everything on the inside of the lock is pretty much the same, functionally, as found on percussion locks.
The flint in the cock, the relation between the cock and the frizzen, and the frizzen spring all combine to make it possible to both produce sparks, and get them into the priming powder FAST so that you can ignite the charge in the barrel. Setting these parts up to work together is the "Set Up" work that is more involved, but considering the problems I have encountered with Percussion locks that didn't go "bang" when the trigger is pulled, I consider all locks to be problematic when first received.
Within 3 years, the majority of members in my club NOW owned and shot Flintlocks, including me. I have never looked back. The only percussion gun I now own is a DBL shotgun.