Most guys live off base - only 2 in my platoon live in the shacks.
Yes, the shacks suck. Your chain of command can walk through your room whenever they want, you can hear yourneighbour banging his girlfriend, there is always blood/vomit/butts in the hallway saturday morning. They are new, just small.
There is always a demand for infanteers, just as there is always lots of guys leaving. Turnover is huge (10-30%) every year.
There's no telling where they would send you if you signed up. They send you to the unit where the need is greatest.
In my experience, guys don't quit as a result of multiple tours. They quit because of the grief associated with garrisson routine, which in some units, demands just as much time away from home.
Hope this helps.