Had my T6 a couple of years, only replaced the battery once or twice, though possibly because I use it mostly as a stopwatch, as the HRM transmitter kept falling off after cracking at the strap holes fairly easily (maybe caused by me ripping it off when I failed to get reception for the hundredth time - though again I've had THAT problem with Polars too). The backlight is also a bit pathetic, and only accessible by holding in the button for 3 seconds - not that easy mid-run!
On the plus side.... I've never had a problem with the Footpod (apart from its depressing accuracy in telling me how much I've over-estimated the length of runs). Software is easy to use and tells you quite a lot - I bought it partly because of the altitude function - surely handy for you proper fellrunners? I'm a bit sceptical/ luddite about the EPOC function, as it would drive me up the wall to adjust training pace according to a piece of software as opposed to feeling/ training diairies. Also quite well-designed - the most compact of all the HRMs/ GPS-type monitors, given the number of features, at the time of purchase - though dunno if other manufacturers have improved since then.