If you were to fit a "proper" (for want of a better description) DRO system based on glass or magnetic scales rather than capacitive readout units, with a mains powered counter rather than coin cell power units, I would not expect them to suffer any harm from being left attached to the machine regardless of environmental changes. I never came across any industrial user who would countenance stripping such items from their machines prior to an extended winter shutdown & cannot recall an instance where such equipment failed due to being left for an extended period in an unheated workshop.
The only items I religeously exchanged before the Xmas shutdown (which could be up to a fortnight in an unheated workshop depending how the holidays fall) were alkaline CNC memory buffer batteries, as depleted batteries may have dipped below the voltage level required to maintain the memory if the temperatures dropped very low + everything got sprayed with Duck Oil to ward off corrosion due to condensation. The Newall readout on an XYZ turret mill (Spherosyn scales) & M-DRO systems on a Harrison lathe (glass scales) & linisher (magnetic scale) in my last employment had all endured several winter shutdowns without any issues, likewise the various CNC systems (variously glass scales & encoders).
As to ease of removal, a glass scale is a screw at each end of the main extrusion + a couple for the read head. Replacement would require the scales to be re-aligned witha dial gauge – less work than the initial fitting,as the mountings would obviously already be present.
Nigel B.