To be perfectly honest, I am about to swap out my Plane Power 30a vacuum pad backup alternator for a B&C. I run the EFII system with the dual-alternator version of the Bus Manager. So both alternators are intended to be online at the same time in normal operations. For further reference, I run a Plane Power 60a primary alternator.
The voltage regulator in the standby alternator never quite failed, but the voltage crept up to 14.6+ volts over the course of the first 80 or so hours of life, enough to cause me to decide to replace the regulator. On advice from Tim at Hartzell at one Oshkosh, since both alternators would be normally on, I switched from the standard 13.8v regulator in the FS1-14 to the 14.2v regulator normally found in the FS1-14B. No problem, easy swap.
It has now been another 80 hours, and I'd say probably another 30 flight hours (another another Oshkosh) ago, /that/ regulator has also exhibited the same behavior. Tim is at a loss to explain, and I am also. I now, at startup and climb, keep the standby alternator on, only to charge battery 2. I get a high voltage warning at some point once the battery has charged, and then I turn off the alternator and leave it off.
Given what I've read in the past about Plane Power and their regulators, much less the bearings, I am probably going to be talking seriously with B&C this coming Oshkosh.
BTW, I run a 40a fuse also. I had a 30a fuse and blew it once during normal charging one time. I have EarthX batteries, which are more than happy to draw full amperage to charge.