A friend of ine has labs. One is 11, the other 12. She says it is a relief to have older labs, as they "only" need a 2 hour walk per day now! When they were younger, she thought nothing of going off on a hike with them for half a day or so, on a regular basis (4 to 6 days per week). She takes them to 3 different places with huge open fields, and they can run and run and run and . . . .

I've heard boxers are high energy, low attention span (for training). How old is the BF's dog? No need to answer, just another factor to work in the mix. If that one is older, it is not going to be helping exercise the puppy much; the humans are going to have to do it!