I've had a few nice cars in past which have been and gone, looking back, I regret not using them more. I'm not convinced you get that much more money and you still have the annual running costs anyway. A while back, I had a 1985 911, sold it having only driven it a couple thousand miles during the two years I owned it and thought Id done well to make some money on it. Turns out, I could have rung its neck for ten years and still made more than twice what I'd paid for it!
Honestly chaps, look after your cars, but don't be afraid to use them, if you really don't want to loose money, don't sell them!