Just some ideas.
1. Do not sync everything.
Define what out of sync is acceptable to you. Let's say 1/10 sec. (I would be way less "picky" and go for let's say 1/5)
Then calculate how many images you need to accumulate that out of sync, and only adjust that. This will be now adjusting only let's say one of every 10 clips.
2. Choose a "multiple" framerate
Final Cut Pro X has a very very easy-to-use feature that syncs up separately recorded audio tracks of the same event that. For those who are confused, recording the same event on two different recorders will yield files that don't sync up perfectly, especially if they are an hour long or more!