My dad had a 4th gen Ltd 4wd for occasional retrieval of off-field glider landings. The 4wd got used infrequently. It would often malfunction from lack of use, with the servo motors seizing. This appears to be a common malady for that 4th gen. The official Toyota repair required pulling the transfer case and replacing the servo unit. More adept owners were able to do a servo unit teardown/cleanup in a few hours with no parts required. Simply running the 4WD through it's paces once a month helped avoid this potentially expensive issue.

Does the 5th gen Ltd 4WD have this same vulnerability? I bought one for occasional use in snow when I visit up north. Will it start malfunctioning if I don't "exercise" the 4WD regularly? It's a many mile drive from where I live to a dirt road where I can lock the center diff and put it in low.

My 3rd gen Ltd didn't have this problem.

The 5th gen Limited is full-time 4wd. It is ALWAYS in 4wd. So no you won't have issues shifting from 2wd to 4wd, as you can't.

You COULD eventually have issues with the ability to shift in and out of 4low, if you don't exercise that occasionally.

My area many decades ago had plenty of dirt roads. No more. Went into the boonies and found a lime rock road. Locked and unlocked the center diff multiple times. Shifted multiple times into Lo likewise. Unless I hear there aren't servo motors prone to seizing due to rust, I'll probably do this monthly.

That being said, all other 5th gens with their part-time 4WD system do still have this same vulnerability, and owners of those remain suggested to through their hunk of junk in 4WD once a month or so to avoid the same annoying/costly fate.

And even if you have the manual transfer case lever, best to let the ADD system run its paces.

Just find a straight road and lock it into 4wd for a while about once a month.