This question is just to give me an idea so I can be prepared for it. I live very Far far away, so I will probably order a couple spares. I Jeep off-road as often as possible weather it be during the week, evening or week-end. and it's rough off-road, through deep mud, tundra, climbing over mountains etc.
All that said how long can heavy duty joints last From drive shaft to the steering?

sounds cold there. i would cary spare front shafts,and spare driveshafts if possible get a dana 44 out of a xj, or an 8.8 out of a 94 or newer explorer,the dana 35 is nothing i would want to trust my ride home from the tundra to.
alloys in front with ox or ctm joints would make the front more trustworthy.
loose the vac disconect.
could do soa /wagoneer axles ?