What are you doing at 30K? I thought your wings melt at that height?
The time it takes to climb up you could be engaging more targets you could spend bullets on. 
When is the last time you were at 30k? If you have been lately then you know there are alot of targets up there. Some are bombers, some are fighters. All of them have invested only a little time and patience to get there. Just like the stuff on the deck, some are good fights some are bad, but bailing when you get engaged at 30k is just totally lame. Period, it's lame. Justify it any way you want, but, it's just lame.
Fights at alt are totally different. Planes handle differently, you have more choices to make, and more mistakes too.
I'm up there too. I see Chalenge around me alot. I put myself in a position to intercept, fighters or buffs, and I see him in that position too. It's idiots like us that stop many buffs BEFORE they drop, and call out inbound missions early enough for some folks to help with the intercept.
My mantra on altitude: "I don't mind fighting on the deck, I just aint gunna start there every time."