as long as you are providing them with clean water and food and shelter they can last for quite a bit. i would recomend getting the dehydrated water cubes/clusters from pro geckos. a great price for the amount that you get.
A crickets life cycle if only about 8-12 weeks total so adults will last from any where from 2-4 weeks depending on how you keep them. They don't last long at all compared to many of the other feeders on the market now. Roaches can live anywhere from 12-24 months after becoming adults. Way more bang for your buck and are much hardier.