A cautionary tale... (a true sotry)
Acouple of years back, the guy over the road was beavering away on his PC, and quite a bit of dust had built up inside it. Being a switched on all the time school of computing he left it alone. Shortly after, it burst into flames, almost setting the house on fire. The fire brigade were there for about 3 hours, they managed to put the fire out, but the entire house was smoke damged. It took almost a year and 4 large skips to sort it out, the electrics were fried and all his furniture was condemed by the local council along with the rest of the house. It took ages to get it sorted out and liveavble again. He was in the middle of doing the house up to sell it, but this put the kybosh on that. Now he just wanders round looking miserable all the time.
My box is in a dusty area where spiders, earwigs, various other flying insects, and the odd wasp reside, but they are kind enough not to have taken up residence inside. I make a point of opening it up every 6 months or so, and using a small paint brush and battery vacuum cleaner (yes they do work) to clean it out whether it needs it or not.
Fire, 'cos that's exactly what happened.