I've always changed my belts every 60K or so. They may not show much wear, but are far more subject to breakage past 60K.
Spend the money for a new belt and be fairly sure it will last another 60K without trouble. The cost of a belt now will far outweigh the cost of a tow and possible engine damage later.
PS. Welcome to the site
76 240D (W115) - 550K miles
78 300D (W123) - 200K+ miles