I have a leaky rear seal in the differential of my 2011 RAV4. Anytime I get an oil change, I have the shop check and top off the rear differential gear oil. Not sure what the millage was when I first noticed it - Significantly less than 100K. One owner.
Do they have to add much? If yes, get it fixed, if not, then I might just keep adding. Unless it’s getting worse.
Is it leaving spots on the driveway?
Or just sweating?
If you have to add any oil, you really should get it fixed. If you or the shop forget, or the leak gets worse, you can destroy the differential quite quickly. It is far cheaper to fix the seal than rebuild the diff.