It is not the pistons fault , all pistons have the same melting point , regardless of being cast or forged , as they are the same material , before the melting point is reached the pistons get weaker , the closer to the melting point the weaker they get by a large amount.
The heat path from combustion is across the piston top then through the rings to the cylinder wall and into the water system ,it also passes through the rings to the oil system .
The piston top is cooled by oil sprayed underneath it .
any carbon build up creates hotspots and can cause detonation, so :
There are a few things that can cause problems , water system must be working properly , pump rad flow ,stat etc , oil system must be working properly, pump ,flow, quantity pressure , oil squirters etc ,carbon build up cannot be excessive , worn rings or very rich running and the mixture/timing and fuel quality be correct , lastly the plugs and valves play their part ,they pull heat out to the head and onto the water system.
Basically it must all work properly together or your new pistons will do exactly the same fairly quickly