I started out with one AC and one DC. I let mine run 24/7 before I heard about hooking up thermostats on the forums here and then they only ran during the warm temps. What I also discovered was that the AC pump brushes only last 1-1500 hours, where the DC should run 5000+ hours. Apparently the AC is more harsh on the brushes. Although I then went to all DC pumps, the 2088, I did have one where the end cap bearing went out on me. At least I could find the end nearing caps with new brushes for about $35 each. Not sure what kind of vacuum I am getting yet, but might put some gauges out next season. I do agree that we seem to get a lot more sap then without vacuum.
220 Taps
2x6 Home made
Sap Shack 20x20
5 Shurflo diaphragm pumps
250 GPH Deer run RO