There's no hard and fast rule really, but don't expect it to never break. Too many people complain about diffs and gearboxes in RWD & 4x4's when in reality its a +20 year old worn part that someone has chucked new seals and bearings in (if you're lucky) and expects it to be bulletproof with a 50% power hike thrown in as well.
I've broken about 5 or 6 of these boxes over the years, even a brand new one from Ford that lasted about 3k miles
and that was only on stage 3 and greens. The last one I detroyed lasted less than 5 miles after I put a T4 on, as soon as I gave it big licks it shat itself. Power delivery, driving habits & maintenance are all a factor, try it and find out, that's the basic answer.
Plenty people run standard boxes on modded 4x4 saphs so I wouldn't worry about it unless it breaks, you can always de-tune it if you blow the box up.