If you have 4 going at once, then I suppose so. I’m not sure of your current set-up, but since you can ferment under pressure, control the temp, and remove sediment easily - you could ferment and transfer to a keg in about 7-10 days. So if you brewed a few times a month, then 1 Vessi would work...

I just joined BF today...yes, I use a Vessi. I absolutely love it. I brewed a few days ago to have something ready for our New Year's Eve party.