I think most people will wear down the rim braking surface before any other wheel component goes bad, but you said you have disc so that is not going to happen. The Aluminum axle XT rear hubs have had occasional reports of bearing failure but you report that you had it regreased twice, presumably you will continue that. Front Shimano hubs often do not have much grease in them, I have added grease to my new front Shimano hubs. Presumably you greased the front too.

Occasionally you hear of a rim cracking in such a way that it probably was related to high air pressure splitting the sides apart. If you stay reasonable with your air pressures, that should not be a problem as if there was any inherent rim weakness, you would have discovered that already.

Bottom line - your rims and hubs might last forever or they might not.

A friend of mine did a cross country trip (cross USA) and said that many in the group had to replace a rear rim. He said his rear A719 rim cracked, but I am not sure why or how they cracked. I consider this as an erratic failure since there are many with similar mileages that have not had any such problems.

I do not know if corrosion can play a role or not, but the friend of mine that had that rim failure was part of a group that had a photo to start their cross country tour, each in the group had their bike rims in salt water at the beach. I am sure that the winter road salt is bad for my rims, but there is not much that can be done on that.