blimps are balloons with engines on them. if you ran out of gas you'd just be unable to control your flight.
you'd also be vulnerable to wind and weather, good luck hitting anyone with the blimp moving all over even in the slightest wind.
blimps can't carry much. you'd still be highly dependent getting supplies every time you land.
flying too low you can get stuck in trees or hit building. flying higher means you're out of range to shoot anything.
blimps are big and light. i dunno how on earth you are gonna store that thing when you're on the ground.
overall its just a really bad idea.
I dont think u would be able to hit anything from that far