I've thought about it before but I wasn't keen on the models that screw over the valve stem (just seems scary to have your valve open all the time); I liked the ones that install inside the rim:
i put mine on march 11th and the pressure has been the same since. it may fluxuate between when its hot and cold but when i get on the bike in the morning its always at 41psi
The instruction say to make sure there are no cleaqrance problems after installing them by rotating the wheel. Most of the sites also sell replacement valve stems (straight).