Hi! - New member, disco alternator query

Hi, new member so unsure of the protocol, but I am seeking advice. I have a Disco 1 v8 converted to LPG before I bought it, it appears to have an appetite for Alternators, so far 3 in 2 years! There are no additional electrical loads, lights, winches etc. Only thing that I am wondering is if the underbonnet insulating mat may be interfering with the alternator ventilation causing it to overheat. Any ideas please? Phil.