I think there is a limit alright. There might be a workaround using G92.
One time I did a job where I had to go about 10 full turns. Then I wanted to cut the other hand of the groove without unwinding and starting over, so I renamed the position at the end of the 10 turns as G92 A0. This was sufficient to fool the control into not unwinding when not desired.
I made several passes during this program and ended up with a fairly large number accumulated in the G92 register. At the end of the program, I commanded a new G92 amount that was sufficient to cancel the total accumulated in the G92 register (which you can view as you page down in the work offset pages). Then, with G28 quick rotary turned on, I could restart the program without wasting any time unwinding from a huge G92 position.
In your case, you might try going 7200° (exactly 20 full revolutions), then interrupt your toolpath at that point so you can insert a G92 A0 command. This will make the control reckon that the A7200 is now A0, and will allow you to go another 7200 degrees. You will need to set up your post or your toolpath so that the maximum commanded position does not exceed the A7200. I'm not sure if that is possible?
All of those G92s will add up, and you need to cancel them as described above before you try the G00 G28 A0 to prevent the unwind sequence.
Make sure when you do this G92 stuff when the rotary table is exactly at the 360°/0° position. When you restart your program, the G92 register should be zero and it must be kept at zero for every subsequent restart. You can also zero the G92 register in MDI.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)