The advice here is spot on. You need a compressor with a higher cfm rating, not a bigger reservoir. To estimate how much compressor capacity you need, take your thirstiest air tool and multiply its cfm consumption by 2. That'll give you an idea of how much capacity you'll need. If you run that tool continuously, your compressor will run 50% of the time.
Example: My inline sander's rated consumption is about 9 cfm at 90 psi. So I looked for a compressor with a rating of about 18 cfm at 90 psi. The 5 hp 60-gallon Ingersoll Rand model seemed to be a good selection for me, so far so good.
Hope this helps.