Having a low range private key could put your funds at risk after revealing the public key, however if your private key is in a high enough range (256 bit range) to this date and for the 10 coming years in the future, there is no danger whatsoever. Think of it this way, your unused address is like a buried treasure, when you use it and send back the change to the same address is like digging the treasure out taking some coins from it and burying it again, now if anyone passes through and sees the fresh soil, they could dig and find it, unless you bury it so deep that digging it out could take years and so much energy.

Above analogy is not completely relevant but it should give you an idea.
More technical discussions here: https://bitcointalk.org/index.php?topic=5434896.0