Yet in over 25 years of using them I've never had one fail through overheating or other failures. One I ran over in the car was still usable - I binned it though. The number of other suppliers plugs I've had to bin over that period due to defects - cable grips, knackered screws, cracked mouldings and general wear and tear is well into double figures. While I'm on about plugs don't get me started on those stupid plugs (duraplug?) where you had to thread the cord through the top before you started terminating - 99% of them on the planet have been cut with a stanley knife just to complete the job!
YPMV
Your plug may vary :)