Do stepper motors require any maintenance?
I've had my printer for almost a year now.
Is there something I should be doing to maintain the motors?
Generally speaking you should never open a stepper motor that you intend to use again - in some of them, the magnets used will be weakened if the motor is disassembled without the use of an iron "keeper". Further, there's a risk of getting contaminants into the small gap between the rotor and stator. In theory, there are ways to carefully do a bearing replacement, but it's unlikely to be worth the trouble on a stepper of the sort used in desktop 3d printers.
The stepper motor itself does not. You may want to inspect the motors for debris or dust.
Depending on your configuration you may want to check on parts of your printer that connect to your stepper motor such as shaft couplings, pulleys, lead screws/threaded rods and belts. The stepper motor wires should occasionally be inspected for wear and strain.
Checking wires for damage could prevent something worse, but is there really any advantage to checking other parts periodically? I think that such a check is only needed when you notice a deterioration in print quality.
Never hurts to preemptively catch issues. Some of those are easy to check. Others require reviving the bed. I wouldn't bother with those since it would require a calibration again.