I think a good easy measurement is keeping your 1RM bench, and your 1RM weighted chin equal (including BW)
If there's any confusion there, say you weigh 200, and bench 300. You should be doing enough chin-up work to be able to strap on 100 lbs and get 1.
Another way to look at it would be to keep the overall work equal (at least), between pressing vs pulls/chins/rows. For the sake of simplicity, lets say you weigh 225, and on a bench day you bench 225 5x5. A good baseline might be 30-35 chin-ups/pull-ups to match it (accounting for warmup). Can play around with assistance/weighted chins, and rep/set schemes to find what works best.
What I've had the most success with is making upper back workouts their own day, they tend to be pretty short though. The last one I did, I simply did 100 chin-ups for time and done.
I did like supersetting back stuff with pressing stuff, ala 5/3/1, but entire upper body DOMS didn't mesh well with my job.
A final note: I don't think you can really do too many pull-ups/chin-ups.