If you're playing within your BR means, there is no problem with rebuying. Now, should you rebuy really depends. You have to consider your starting BBs if you rebuy and how you'd do in that position. Rebuying and have 50 BBs to play with is a lot different than rebuying and have 15 BBs. Are you capable of making those adjustments necessary to be successful?
If you're near the add-on break, I think rebuying is worth it if you're planning on taking the add-on. What I do when I play rebuy MTTs is I always register during the break and take the add-on option. By doing this, I minimize my buy-ins into the game and since late registration has ended and I'm practically just late registering into a standard MTT at his point. At the micro-stakes (where I play) players are playing a little bit tighter as, usually, it's not too far from the money money bubble and many players are trying to get ITM. Fast, loose play has reduced significantly as buying back in is no longer an option. And if you're able to play a mid-low stack effectively and take advantage of the weaker players, you can potentially do well.
Using BOL as an example, registering during the break and taking the add-on gives me a ~27 BBs to start, ~37 BBs if I'm able to take the rebuy option before the add-on. Most of the time, at 37 BBs is around average stack size with very little effort.