I personaly think that the quality of the pumps has gone down , I am still using a shurflo from 11 years ago , it has not even had a pressure switch replaced yet !
It started life coupled with a Varistream analogue which only needed the blue dial inside knocked on or back a single click between summer and winter , that lasted for 5 year .
Then it got treated to one of Mr sheppards original controllers ( the one without auto cal ) , that served me for 5 years also , very rarely needed calibrating until that gave up the ghost last winter due to the circuit board saying "I've ad enuff mate , my solders have had their butts cooked "
I told Ian last year that I would defo buy the latest model , but as I sponged a £7 china controller off my brother to keep me going it has not happened yet , but it will as its just coming to light now that the lack of calibration settings is causing rather large amounts of back pressure due to pump over run ,
Honest Ian , I will get one this year , hot water has done you a favour