Load Range E tire pressure: how do you keep them up?

Thanks everybody. My last maxxis's didn't lose much, just down 1-2psi from 50 every 6 months or so. That said, my cheapo harbor freight 3 gallon compressor doesn't exactly make short work of topping them off. I can't imagine how it would labor to get from 77-80psi :-0
Rather than getting a dc compressor, maybe I'll just get a stronger one for home and keep my fingers crossed I don't need to air up afield.