This depends on your paint booth’s heating power. If your paint booth is direct fire and has heat recycle, the paint booth should both get to temperature in a few minutes and maintain a higher temperature like 150-175 degrees Fahrenheit. This should allow you to comfortably paint and cure a job every hour to hour and a half. The “real” IT DEPENDS attached to this answer is the biggest variable in your shop… YOU.
HOW you run your shop or facility in terms of flow is the number one factor in how many cars or jobs you will get out a day. If your shop is a well-oiled machine that constantly has a job ready to enter the booth for finishing, then you will push the limits of your paint booth’s hardware and power. 9 times out of ten, the paint booth is WAITING for work due to slow or disorganized shop flow. Consult with your closest people and develop a smooth flowing line that will use your booth’s capability to the fullest. We see some people do with three booths, what another facility does with one. Definitely invest in a machine that can keep up if you get organized and start crushing it. You never want to be held back by your paint booth if you develop a great cycle time so always buy based on performance, but before you turn your attention to the paint booth, shop flow is number one.