There's not a lot to worry about ... as far as the motor itself is concerned. The right motor, installed correctly, will not only run darn near forever ... it will give lots of warning when it's getting tired.
There are three phase of maintenance:
1) Verify the selection;
2) Check the install; and,
3) Keep testing records
You verify the selection by comparing actual voltage and amp draw to the nameplate info. Check the running temps. As Rod said, keep it clean.
The motor has to be properly mounted, with the shaft/sheaves properly lined up. Belt/chain tension ought to be correct.
If you have a megger, there are a series of tests you can perform. These tests, for the most part, begin when the motor is new, and are periodically repeated. Comparing the results over time will give you ample warning that the motor is about to fail.
