Back-up Bow...is it necessary?
I have my original bow I got about 15 years ago. Can't sell it for anything, so I keep it around for a back-up. Pretty cheap insurance in my opinion.
Whether you really should have a back-up bow depends on lots of factors. For one, if the money you could make from your older bow would make an impact to your financial situation (e.g. it would help be do X or offset a cost Y), then maybe it makes sense to sell it. Same could be said if you hunt only occasionally or feel it wouldn't be the end of the world if you had a mechanical during hunting season.
On the flip side, there really isn't anything bad about having a back-up bow, other than the fact that bow may collect dust. Murphy's Law always seems to drop in unexpectedly when the hunting seasons roll around. If it does, that back-up bow may be your best friend.