Posted before finishing my thought process...

VMWare and VirtualBox both offer snapshot capability.  Personally, I create at least 1 snapshot each day, and keep a full backup of the VMs on a set of external drives that I rotate out between home and work (create backup, bring drive 1 to work, take drive 2 home, etc...).

Remember that you're basically carrying your bank account around now, and every time you browse the web or install something on the same machine as a wallet, you're trusting someone else to be left alone in your vault.