Thanks Guys. That was what I was afraid of... not OK to leave them in very long.
The hard part is that a lot of the time I put parts in to run and then I go outside to work for an hour or so while they do their thing, so Im likely to not even know the power is out until I go back to the shop. I suppose I'll have to rig up a big loud battery powered siren to alert me when the grid goes down. Unless it's on the weekend, then my wife can perform that function for me.
Thanks,
Steve