Been wheeling Dana 30's with 33's for over 25 years.
On my red Scrambler, 33's, OX Locker, chrome moly Dana 44 shafts, internal spline hubs, 4.10 gears, over 39,000 miles of highway/wheeling, no problems. Three trips to Utah, two trips to Michigan, ORV parks in Arkansas, Kentucky, Alabama, Louisiana, etc etc, no problems.
33's, moderate horse power, common sense, hard to difficult wheeling, no worries
Any of the above changes, maybe time for an upgrade
Our version of the Dana 30 really isn't all that bad. I know people who have been wheeling them for years, locked, on 35"s up here. The 6-bolt hub is really the only thing that I believe is worth doing.