Spokes require that they be tensioned within an acceptable range and most important is that the tension of each spoke is equal relative to the spokes on the same side of the wheel... cassette wheels are dished so the non drive spokes run at a slightly lower tension than the drive side spokes and a common mistake is for people to tighten these thinking they need to be as tight as the drive side spokes.

Non dished wheels like front wheels and rear wheels with internal gear hubs and single drives usually have no offset and the spoke tension on each side should be the same.

Even when those spokes are tight and rigid they are not static and need to withstand many thousands of stress cycles, a loose spoke will fatigue under repeated stress cycles and this can happen rather quickly.

A well made wheel will require very little attention, if any, over it's working life and if one is using rim brakes the rim should need to be replaced before the spokes need anything.

I build my commuting wheels like I do touring wheels as they have to withstand a lot of abuse and when you are depending on your bike to get you to and from work you want to know the wheels under you can take anything you throw at them.

If a rim develops cracks it needs to be replaced immediately as this is a sign of extreme failure that may be unrelated to the spokes and the build although in some case over tensioned spokes can pull a nipple through the rim.