Here's the rule of thumb.

Anything over 120 degrees, you can touch, but you will have to take your hand away.

Anything under 120 degrees, you can keep your hand on (of course till you get too cold).

The servos are rated at least to 150 degrees cause I have temp probed them at that temperature before.

Now, for the "touch" test of a fuse.

Fiberglass starts getting soft at around 155 degrees. So there is some temperatures in between what you can't keep your hand on, but is perfectly safe for your airplane.

Best to have an IR temp sensor available on new install first runs in case your install puts you in the range between 120 and 155.

I have seen prolonged exposure at 145 that did nothing bad to the airframe, but you could not keep your hand on the fuse.