Once the tank is up to pressure, the compressor will have to run to replace what you take out, so the overall compressor duty will be the same If you take out 100 cu ft the compressor will have to put in 100 cu ft. The potential advantage will be you could take out a large volume in a short period of time and then the compressor would take longer to refill. If you have times when you need higher air flow than your compressor will provide it's a good solution.
