Depends how fast/slow you ride 600ks. My 800 was fine for all the 24hr races I did and most of the long training rides I did last year. Like I said, it only died once and that was during my longest ride ~30hours.
External battery, no route calculations, 1s recording, record to SD, um loads of settings. No idea what causes the failure. The one time it did die I was using navigation to actually follow a route and had changed external battery once already. Probably a mapping bug.
Depends how fast/slow you ride 600ks. My 800 was fine for all the 24hr races I did and most of the long training rides I did last year. Like I said, it only died once and that was during my longest ride ~30hours.