Of course, the post immediately following mine reminds me of the one exception to my "hoard everything" rule.
While I did paint at least a few of the Space Marines that happened to fall into my possession, I had absolutely no qualms giving them away as soon as someone expressed even a vague interest in the faction. I dunno if it's the over-saturation or the Mary-Sue-ism or what, but those ceramite-clad fascists have zero appeal to me.
I have painted thousands of minis but never completed an army, the closest i have come is a skirmish force for Westwind's SOTR. I suffer quite badly from "the hobby butterfly" projects getting shelved part way through then when i am in the mood to go back to them my painting has improved and i start again with fresh minis and a new scheme.
"This lighthouse is under attack - and by morning we could all be dead" The 4th Doctor - (Tom Baker) - Horror of Fang Rock
I struggle with painting Space Marines. Me and flat areas just don't get on. In the end I managed to do a pile of them by airbrush which looked fairly good but if I wasn't painting to sell then I wouldn't be able to live with them looking like that.
15mm! I've tried Naps, FOW, ancients, sci-fi. You name it as a period i've probably tried it in 15mm and thought it can't be that bad painting something smaller. I start off great, clean the models, undercoat them, sit down do about 2 hours of painting then my eyes start to hurt. I just can't concentrate on things that small (somewhere the ghost of Frankie Howard is going "oooh errr missus"). I've tried the big magnifying glasses, adjusting seating positions, natural lighting. I keep on wanting to do the scale as I lack space but I think its just never going to happen.
.. I think that the poorest he that is in England hath a life to live, as the greatest he; ... and I do think that the poorest man in England is not bound in a strict sense to that government that he hath not had a voice to put himself under