I don't know a ton on the matter. However, I do know that they build in some off days. I am a huge Spieth fan, so for him at least, I know that a practice day is a lot of short game drills and less whacking balls. His level of practice is of the highest caliber. There are some videos that his coach put out on his practice drills that have me longing to practice. Below I will include one of the videos.
m.youtube.com/watch

Here is a video of Jordan Spieth describing a practice day.
m.youtube.com/watch

Hope this helps! Enjoy your practice!
Jack

At last years US Open at Oakmont I spent a lot of time watching the Pro's go thru warm ups and after round practice sessions. Comparing those guy's to amateurs at the range the main difference that stood out to me was the time between their shots. The pro's are in no hurry, usually several minutes between shots, they also watch every shot from start to finish, they talk with their caddy's and coaches a lot during their sessions. I didn't count how many balls they hit but I'd guess that none hit as many as you are during a session. Course that was at a tournament, they may have practice days where they do hit a lot of balls.
You're making as many swings in a range session as a pro would during a whole tournament, you have great stamina, I couldn't do that.

There are a lot of great videos on You Tube that go behind the scenes and show you how the pros practice. It's different for everyone.

That really is a very good question, shame some of the pros can't comment and say how many they hit and how they like to practice

This is good:

www.youtube.com/watch

There are a whole bunch of these on youtube

They probably hit around 500-1000 balls a day when practicing.

To quote Gary Player, if you practice 3 hours, spend 2 hours on short game. Practice your shot routine while on the range. Doing that, it would take close to 3 hrs to hit 150-180. Then add another 30-45 minutes putting.

One thing I notice when watching pros at any tournament, is that they take two bags of balls, about two dozen, and work thru the bag. They mostly hit or practice shots that they will need for the course. A high fade, low draws, with diffferent clubs. During the practice or pro am rounds, they practice putting on each green where they believe the hole would be on Sunday.

The PGA tour YouTube channel has a lot of videos on the pros practice sessions. I love the detail in them. I suggest you check them out !