I have never participated in a Mini Ludum Dare, but anything that encourages you to recycle/finish/polish old games is a good thing:

> You may use old unreleased code/gfx/sound if you made it by yourself (No copyright infrigements)
> You may rebuild any of your old games to fit the theme. See above
> Theme will be Disclosed before the compo begins.

Sounds very pragmatic. Under these circumstances, I may find half a day or two to rework something old :)

http://www.ludumdare.com/compo/2011/05/10/announcing-minild-26/