Three weeks complete rest but then 30 days to essentially retraing your voice because usually singers have adapted to the damage and developed bad habits because of that. Paul Stanley sounds much stronger after his surgery last year and Don Dokken raved about the rehab which he said surprised him how many bad habits he picked up. Have not heard him sing since his surgery.
Doing that surgery mid tour would be very unlikely but not impossible.
I think 2007 Dave was much more disciplined with his mechanics