If you’ve been tempted by these gadgets, or if you’re actually thinking of trying to create one, please, please don’t. There are gadgets you can get which will essentially keep temp-on-rez items permanently alive (basically they re-rez the items every time the temp-on-rez reaches its time-out). Unfortunately it is sometimes used as a way of circumventing Second Life’s prim limits. It is a very handy feature with a number of legitimate uses, the most common of which I suppose are bullets and vendor displays (which temporarily rez examples of the items for sale).

Temp-on-rez is a prim setting which will keep a prim ‘alive’ for a fixed amount of time, after which it will be removed.