I say if he is eating mice just fine, keep him on them. Reptiles aren't "cheap" pets by any means.

Also never, NEVER, NEVER force feed a snake that is willing to eat on it's own! That will only cause the snake to really stress out and that is not a good thing. The only time I can ever see or think of that force-feeding would be a good thing is when a snake is really sick or you really have a non eater and it's in one of those life or death situations when it really does need to be fed.