by warn locker hubs, do you mean the manual locking ones up front with the twisting acutator? if so, then yes the older models all had manual 4x4 engagement. i never knew the technical name though. it is definately good to lock the hubs and put it in 4 low every once in a while to keep things kinda lubed and make sure they are running. id say once a month, but you can get by with once every 6 weeks to 2 months or so.

i had my 89 for 13 years and the only thing that went 'bad' was the exhaust was starting to rust out, and the usual tire wear, but the truck only had 64,000 miles when we sold it because for most of the time my dad has a state vehicle and then i drove it after i got my license.

id say your normal tune up and transfer case gear oils should be checked and changed if needed and check the chassis lube points. other than that the motors themselves are very stout, but not the most powerful in the world.