How many miles you guys got on your 2.9s? What's your BII's primary use? Just wondering.
Ours is an 86, just used as a secondary daily driver. Low mileage for how old it is, 106,xxx last time I checked. We keep it in good shape for it's age, even though the body itself needs a new "cheap" paint job in the future maybe; sits outside in the sun.. so the roof is a little rusted and cooked as far as paint goes.. and the front fenders are rusting a little. Chassis is pretty rust free, and the motor still runs good, trans and transfer case are still in good shape. It doesn't get driven a whole lot though.
Doesn't burn any motor oil, or atleast enough to notice. I'm pretty sure it has the infamous lifter tick and has had it for quite some time, sounds almost like common day Ford injectors and how they tick when they pulse. It's not too loud.
Other than that, can't complain other than usual stuff wearing out over 21 years.
BII 2.9 durability/mileage?
How many miles you guys got on your 2.9s? What's your BII's
well my bronco II is an 1989 4x4 2.9 liter and it had 205,000 miles on it when i cracked a head driving home from work, it was a five speed daily driven, and used for offroading, of course it had a leaking valve cover, an awefull miss in the motor, and the rear main was leaking 
.. 
so i did the 4.0 switch which really brung my old bronco back to life, considering i used the same transfer case, transmission and clutch parts that were attached to the 2.9 Liter in the Bronco II already....... of course mine has been treated rough over the years, and the dreaded lifter tick......well if it ticks its the lifters im pretty sure because when ford designed the 2.9 Liter block the castings were slightly offset for the lifters, in the sense of how they hit the camshaft, it wasnt corrected untill after they quit producing the Bronco II with the 2.9 Liter ....... the main reason in 1990 they produced some Bronco II with the 4.0 Litre as the stock motor...but it was an extremely limited amount produced before they started making the Ford Explorer in march of 1990 which was released as the 1991 model Ford Explorer....... although some bronco owners report adjusting them i never adjusted mine, but as i said it had an terrible miss, and was just worn out.....but it was treated rough... dont know if that helps any ..... but i know mine still ran with 205,000 miles on it even with the cracked head, leaking main seal, although the lifters rattled like all get out, but i drove it to work 40 miles one way every day......