The only time I have wrapped my cables in foil is when I use the TBE. That gets pretty hot and it was suggested. Well worth being cautious vs having to buy the new cables.
That said, I watch out for deals. I was at a competition where, if I bought something from Maverick, I got a cheaper digital thermometer free. It came with 2 of the cables. I could care less about the back up thermometer but the cables on hand - yep!