Yep. Pretty easy to answer. You can take it off as long as the car isn't running and everything will be okay. Unless the gaskets are reusable for your valve covers (meaning they're thick rubber peices and obviously not meant ot be thrown away) you'll need to splurge on a $5 pair when you put it back together.

If you try and run the car without the gaskets OR the valve covers themselves....umm...just don't do it.