Haircuts are about 3-4 weeks for me. But I am really pushing the boundaries of military regulations by the third week, so I try to skate by another week. I am 23 and going bald extremely fast, so it pains me to cut the hair I have left. I am surprised no one has called me out this week, because I am out of regs for sure.
I tend to go 'skin fade' on the sides and back, get the stubble take off of the ears, leave the sideburns, and have the top trimmed a bit.
Shave? Monday through Friday every morning, unless I am TDY or on leave. Every couple weeks or so I will decide to not shave on a Friday and claim I forgot, if only to get a nice infant beard going for the weekend, but it is definitly noticable.