If there's not a problem with maintaining the caches, why not just let them be? If you want the containers for other caches, just swap them out with cheaper options. The fact that there are long stretches between finds may be a concern, but they will be found now and then. I have several caches that are found very infrequently due to their remote locations, and one urban one due to its difficulty. I just let them be, and when someone finds them, it means more to me that someone took the extra effort.
However, it is up to each individual what to do with his or her caches. When you hide a cache, you should plan on leaving it out for at least 6 months. After that, it is your call. I would advise you to disable a cache a week or so before removing it, however, to prevent exactly the type of thing that happened with IRBH.
"Wildness is a necessity." -- John Muir
"When you go to hide a geocache, think of the reason you are bringing people to that spot. If the only reason is for the geocache, then find a better spot." – briansnat