The policy these days is that the leave is there for a reason so needs to be taken, although you can accrue up to two years if you have a particular reason. Many of us have at least that much due to lack of opportunity to take it, although in my group at least this is slowly being addressed.
Leave planning is done 18 months in advance so if your best mate wants to involve you in his wedding extravaganza he'd better give you plenty of notice! Leave slots over popular periods such as Christmas and school holidays are tracked so if you got Christmas last year you probably won't be getting it again for a couple of years.
You won't get the extra week for 24hr shiftwork until you have sufficient ratings to actually do doggos (night shifts) so it might take a couple of years.
Long service leave is the standard 3 months/10 years. Good luck in being able to take any....