We test our gloves every 6 months; some every month. I once sent more than four dozen pairs of gloves for testing, and 28 FAILED.
Lots of things cause glove failure, mostly improper storage. They MUST be stored fingers up (to prevent stuff from falling in) in canvas bags with the top flap snapped closed. The bag can't be left beneath the rest of the stuff in the hot work kit or anything else, and can't be stuffed in a job box or truck box. They shouldn't be stored where the temperature will exceed 95 deg. F. They MUST be used with the leather protectors, and if they aren't, they should be sent for testing as soon as the task is completed.
Insulating gloves can save your life, but more likely save you from losing months of work while you lie in a hospital burn unit, maybe losing the use of part of your master hand (not to mention disfigurement). You want to risk that to save your boss a few bucks?