If you Mean the 3 Mosfets on power Side, the original ones from IRF (IOR), mostly all mosfets produced by IRF in SMD have the max operating Temperature up to 175 C°.
And for Soldering max 300 C° at 1.6mm from case for a maximum of 10 seconds. The better sollution is to replace the original mosfets with Dual Cool ones. Like the ones in my list or in the list from "J4bberwock".His list is really the best , if you want to go to the limits. This ones have 2 heat pads over/under , so the heat is better get outside the case. And adding a Fan for the powerside counts a lot.
But its highly recomended to replace the 16V Cap with a more serious one , if you don´t have.
Ok, thanks at around 6.6Mhs the max my mosfet chips got to was 143F peak on the
heatsink and dropped down to 139F once the unit stabalized at 1024 share difficulty.
I switched out my 16V cap and put in a 35V one instead, 0 ohm resistors in place of
the ferrite beads.