I will just explain on the example. Are you listenning radio, mp3 player, or TV regulary? Are you aware if they worn out? I think not too much.

Back to computers:
There are parts which are mechanical like Disk drives, DVD etc... extensive using of these parts will worn-out them and they more probably can failed.
But there are eletronics parts which can be damaged only by high current or voltage. The most critical thing is environment. Miner and high end PC is very powerfull and is producing heat which can damage it. But generaly I would not too much care about usage of Miner or PC continuously if you keep proper environment within specification. From experience it`s murch worst to power down and up again and again.

You can choose your Miner to be standalone machine which do need PC, just connect to your home network. This way your PC will not worn-out thanks to mining.