I opened a support ticket.
After the update the battery actually runs out after 3 hours, already tested 3 days of playing.
Before the update the battery works for 6+ hours in the last year without any issue.
If this is the "normal" effect of the new firmware / overheat fix, this is NOT acceptable at all. There isn't also any advice on this or specification on the firmware release notes, Line6 just say that fix the overheat, but not HOW actually this is done.
If Line6 has sold defected units for 4 years, needs to refund the customers or send a new replacement units, not just cut in half the performance of the product.
Anyway, I'll waiting for a support ticket reply in order to evaluate the situation.
I was a very happy G10 (loved it so much) customer until this new firmware.