I've been mining on a "budget" gamermax 1650w psu since late 2017, I have 5 of them, non of them have failed on me so far. Maybe I'm "lucky", but I never clean them, they're dusty af lol.
They are going to die soon if you don't clean them it may block the fan air and the temp of your PSU will increase that could lead to damage/overheating.
I always clean my mining rig PSU, the motherboard and GPU to keep them cool so that temp is always low or on an average temp to increase the lifespan of all my mining rig parts. For now, you are lucky but I suggest you better clean them if you don't want to replace them with a new one.