compressor spec questions

i have two thomas 337 compressors, one of them took a dump, i have had one for 5 years and the other for 3 they have done really good good during this time, all i no is they are 30% duty cycle, so my question is what do you look for when buying a compressor, what is duty cycle, i see 30, 40, 50, 75, 100% but not sure what that mean i do know it took awhile to fill my tanks longer when they were emptied, i know what cfm is so i would want a higher cfm, someone told me to stay away from viar, i realize everyone has there own opinions so lets hear them.

Ive heard go with Viar and stay away from Air Zenith. I got 2 Viar 480s and like em. Ive had em for about a month or so.

I myself dont really understand the duty cycle % though.

duty cycle is how long u can run the pump constantly 100% can be ran nonstop with out damaging the pump. where as lower duty cycles require breaks for the pump to cool and rest. as far as electric pumps viar is the way to go for reliability. if you want the best you go with an edc which has the highest cfm you can get and can run nonstop