from what Ive read stock size shafts only offer something like 20-30% more strenth over stock.
Yes you can run 35's on it but how careful you are with the Jeep depends on how long it last.I have a friend who trail ride and mud rides a stock D35 on 35's for the past 6 years without breakage,then theres others who broke d35's with 33" tires.
breaking a d35 depends on alot of things.personally I'd save my pennies for a superior super 35 kit with the locker of your choice,then your shafts will be stronger than a stock d44 shafts.
my 2 cents.
run it till it breaks,If your running on street or lite trail it may be o.k.,If you have a locker already I would'nt do it unless I was prepared to super 35 it.
also a 6cylinder vs 4 cylinder plays a part also,i would think the 4.0 would break axles eaiser than a 2.5 can