You Can't "Overtrain" Your Upper Back
The benefits of training the upper back and scapular muscles as often as possible far outweigh the disadvantages.
The muscles of the mid and upper back are responsible for keeping the spine erect, pulling the shoulders back, and fulfilling these postural demands all day long. On a basic level, it would make sense to believe they're more slow twitch dominant, especially compared to other muscles of the body.
That's one reason they tend to have a higher resilience and better recovery time, fatigue less quickly, and can take a higher weekly training volume compared to a muscle group like the chest or hamstrings.
We should also cater to these strengths in the name of development and performance and train the upper back for high reps. There's never really any need to do fewer than 10 reps.
Row variations, pulldowns, reverse flyes, single-arm pulls, and everything in between get a prescription ranging from 10 reps all the way up to max reps.
Pull-ups and deadlifts (if you want to view deadlifts as a back exercise).