Kev, while in traditional terms it would make sense to hold them long term, the game is changing drastically now w/ the introduction of new tlds as well as the opening up of 1/2/3 letters of existing gtlds and maybe even other cctlds after the release of .de
If I had access to unlimited funds, I'd lock them away till you can sell each for $x,xxx.
But then, it all depends on what it costs you to renew them and hold them for the four figure sales, good luck.