Routes should not be created or changed often. People need to rely on transit, if they can't be sure their route will still be there for long they should buy/drive a car even if there is good transit today since they will need that car when the routes change to something that doesn't work.

changing routes is needed of course. Cities chanre and you need to follow that. They don't change fast though. long term routes also drive change as people adqust their life to what they can do.