Thought I might mention this. Using a ball machine hitting dead balls is one of the toughest things you can do to your arm. Also difficult on the arm is early morning play on the clay courts where the balls pick up moisture.
Absolutely. The best thing for TE (or post TE) would be only hit with a new balls every time out.
I use Pro Penn Marathon in the ball machine. I open new cans in spring. I always expected to need replace mid-summer, but surprisingly never need to until following spring. I kid you not ... the balls are not even close to dead. I have no idea how that is possible. I always play matches with a new can of Pro Penn Marathon, but they would be better in the second match then most other balls brand new. A friend opened a can of Wilson US Open balls in one match this summer. Lower bounce ... but good until second set. I really think my ball machine balls were more arm friendly.
I was worried about the ball machine sessions in spring coming off TE. I hit a lot of balls with Velocity, and never had a single twinge. I hit a couple of sessions with Cream ... and had a twinge the day after (why I'm not playing fb Cream now as my string ... I loved it). So finished summer playing a ton of singles with fb Velocity, and zero elbow twinge/signs. I assumed I'm 100% … so try Bsseline @45. Arm and back of hand felt sore and fatigued for 3 days. Not pain ... like TE pain ... but obvious signs that I never saw once all summer with fb Velocity.
The ball machine actually presents a related string challenge. I want one of my V1s to be for the ball machine, and the other for matches. I obviously need a arm friendly setup for the ball machine. I really don't want different strings for bm and matches ... the bm is practice and best practice is with same strings. So fb Velocity solves that ... I just have to let poly go.
Edit: I have massaged my forearm and tricep the last couple of days. I haven't needed to do that for months. When I poked around on the forearm with my fingers I found two major sore spots. All from one poly bm session. To me, there is little doubt poly gives our arms and elbows more strain. Many can handle it ... but that doesn't change the fact it's more strain. FYI.