I have two 122cu. ft. bottles. One bottle will last a pretty long time depending on how often you hit the switches as well as how high or low your regulator psi is set, and what size lines you have(I have 3/8). I once went through a bottle in 30minutes(almost continuous use) on a Saturday night. The longest I have went on one tank is about 2 weeks. If you like to air out everytime you park and at a few red lights while driving one bottle will probably last you a week(don't forget to close the valve on the bottle each time you are parking for more than about 10minutes because the connection at the regulator will more than likely have a very slow leak). You could also get larger tanks for more volume but they will respectively be heavier and cost more to fill. I got my rack, tanks, and regulator from EKMW but you could probably get the tanks and reguator from just about any welding supply shop. I get my tanks filled at welding supply shops and the price is about $15/tank for nitrogen and about $32/tank for helium for the 122cu. ft. tanks. Yet another factor is some welding shops fill the tanks to 2500psi while others may only fill to 2000psi.