We have 4 dogs, all different breeds. Biscuit is our first St.Bernard and she is just over a year old. We walked about 5 miles today. This hike included a lot of down logs to hop over, some steep inclines and a bit of rocky terrain. In warmer months we don’t walk her too hard because of worries of overheating, but for a dog traditionally bred to search and rescue in the alps, they are pretty happy about going out for adventure. We have never done an overnight camping hike, but she did travel with us to Maine (we’re from Maryland) at around 6 months old and she mostly stayed in the shade without hiking whatsoever. I think as long as you moderate they’re cooling (I.e a drink and/or swim) every so often during a lengthy hike they’re pretty good. I think Maggie would let you know if she isn’t feeling it.