I've never had a mantis die after eating a cricket, but they aren't my first food choice for most adult mantids. I only use them when I have to. My adult female Deroplatys dessicata would not eat anything except crickets and grasshoppers. She lived a long time as an adult, though her ooths never hatched, and she mated several times with one of her two roommates. I didn't gut load the crickets before I used them as feeders, but they seemed to be healthy and uneaten ones would live in the terrarium for several days. I would occasionally put lettuce and cricket food in the terrarium if I noticed uneaten crickets. Other than that, I only use crickets for emergency food when I'm low on other feeders...especially in the winter when I don't have access to wild caught insects.
In my opinion, a varied diet is a good thing. So, I wouldn't feed a mantis only crickets unless that is all they will eat.