Saving machine settings between sessions

[Neale]

If you don't have good Home switches

My 3D printer uses small microswitches and I have had problems with one of those - the z axis needs repeatability to better than 0.1mm and it struggled to achieve that. I'm going to change to optical switches for that machine. What kind of performance would you expect from the kind of proximity switch that seem to be very popular for routers? Any recommendations? Accurate homing is part of the "save session state" process, I guess.