My father spent most of his life working as an Internal Grinder and Horizontal Borer, although towards the end his time was taken up with Vertical Honing. Me, I used to order an enormous number of EL34 valve tubes for a spectrophotometer that needed one per year when I had a Marshall 100 amplifier. And I knew a man who got away with buying a caravan as a business expense (said it was a temporary office).