Here's my philosophy:
1. Think camping rules - Always sell a pin in better condition than you found it in.
2. Dont ever think of it as an investment, think of it as being part of a worldwide preservation society
3. If you have more projects than you can ever possibly handle within a reasonable time, don't horde them in storage, let someone else have a crack at it
4. Always be honest and up front with absolutely everything in a pin's condition before you sell it (good or bad). If more of us did that, we would rarely hear about "that bad seller" anymore.

I like the cut of your jib, toyotaboy.

I just wish people spent more time loving and appreciating the pins themselves, rather than the pile of money they think those pins represent.