I'm pretty careful, I spend as little time in a guard zone as possible, and even if the server goes down, I only train when I know I'm going to be around to be back on when the server goes back up (as long as it isn't over three or four hours...). I also never tell any unbonded pet to guard me while I am in a guard zone, heck, I don't even get bonded pets to guard me while I'm in a guard zone, or if I need them to be green for some reason, I just say "all guard me", and immediately "all stop" afterwards.
I used to always have my pets guarding me when I pvp'd, to keep them green when fighting with allies, but there are some nasty flagging bugs with guarding that can be exploited, so I don't do that anymore. If I need them green, I "all guard me" immediately followed by "all stop".
If I lock up, unless my computer completely blows up, I'll be able to get back on long before the elemental could kill my dragon, and if my computer completely blows up, that dragon will be the least of my concerns...