This is more for the newcomers---- the old-timers here already know this stuff. It's a very common question that if often asked here. There may have likely been a way to accommodate some changes to the Favorites Lists automatically, but it would have been so complex and convoluted that it would have ended up defeating the purpose for the creation of the lists in the first place.
I have really come up with no easy way, having about 40 Favorites Lists, so what I do is each time I update the main database, I take an extra moment to manually update 2 or 3 of my FL's. I keep them pretty much in alphabetical order on the radio, so the first time I will do the A, B and C lists, The next week the D, E and F lists, and so forth. You get the idea. It is not a simple chore.
With Favorites Lists, I believe that there is a point of diminishing returns. Where the result does not justify effort. I guess it all depends on one's listening habits and one's listening environment. I don't really need 40 FL's--- in reality, I generally only use 4 or 5 at at time.
It's a situation that is similar to "Priorities"---- if you have too many, then everything becomes a priority and it ends up that nothing is really a priority.