Thanks very much, that is really helpful. I have an electronic switch, one of the optical ones that uses beam-break sensors to detect a pressure gauge needle, so can set the difference between cut in and cut off to as close at about 15psi difference. I can easily increase the pre-charge a bit to reduce the stress on the bladder, that makes a lot of sense, thanks again.
I can say that I'm impressed with these optical pressure switches. I was taking a risk in buying one, as they are Chinese, and I have a certain wariness when it comes to Chinese stuff, but having had a UK made spring-type pressure switch fail from frost damage within a year, I saw these Chinese ones for a lot lower price, so bought one to try. It was cheap, but surprisingly well made. I took it apart to see how it worked, and check out the quality, and was impressed, so I bought a couple more as spares. They were cheap enough to just keep in the cupboard if I need them, and have the big advantage of being really easy to set (you can independently set the turn of, and turn off pressure with a screwdriver in a couple of seconds).