That all sounds good. The intensity of the punching will dictate the duration and recovery. But these are all factors to be manipulated at different stages of the year as your fitness progresses.
I liked the “boxing” because I think it helped develop upperbody power-endurance. It was a bit of a bridge from the weightsroom to the track.
It also, I thought (and recently had a scientist confirm), helped evolve the blood chemistry in a way which was similar to what was happening during 400m running training - but in the case of boxing it gave the legs a rest from the striking on the track.
So there was generation and tolerance of “lactic acid” going on, but there was also generation and tolerance of protein breakdown which is a whole other thing again.
There is a deal of protein damage in sprinting and boxing and it seems that this is much less a factor in some other high order aerobic activities such as cycling (although I’m sure if you cranked up the resistance you’d mess up your legs, but then again by opting for some cross-training that’s what a sprinter should be trying to avoid since so much of the real sprint performance involves pounds the legs).