I notice others boasting of 12 to 18 month battery life on the Honeywell Evohome radiator stats but what are users of the Wiser system experience? I've now started to keep a note in a spreadsheet when I change the batteries across my 13 radiator stats and 1 room stat but it does feel like 2-3 months is the most I get in the most used rooms. Anyone else's experience different?