As a former IP, I'd say that if you don't have a problem with your instructor, don't change. It can cause problems for your IP because if students ask to drop him, then the company starts to question why. Also, the later twin-engine Steps are kind of a reward for the IP who labors through Step 1 and is basically an accountant in Step 2.
If you have a problem with your instructor or if you just don't get what he is telling you, an IP change may help. Otherwise, if it aint' broke, don't fix it. You may wind up with someone you like a lot less and be stuck with them.