Gaskets don't need to be changed on a preventative basis and you should always use new ones when you have taken something apart.
If you replace the rings before something bad happens it will be an easy job and only the cost of gaskets and rings. You also get the opportunity of doing the work on your schedule.
If you wait until the engine stops running:
a) If you are a long way from your truck, you could be in a world of hurt.
b) It definately will not be a good day
c) The cylinder will sustain damage, requiring some combination of sleeving, boring and/or plating which can cost hundreds of dollars.
d) There won't be any option but to change the piston.
e) other parts could get damaged, such as the head or even the bottom end.
Rod