Hell, I leave mine on. I have seen 6509's up for 5 years without one single reload. That one was in a production environment.
However, I usually need to erase the configs for different labs. Sometimes it is easier (sometimes) to leave the config-register to 2142.
/
tim@tim-laptop ~ $ sudo apt-get install windows
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Couldn't find package windows...Thank Goodness!