Hi there,
I think you have a while before you start leaking. When I was pregnant with number 2 I never leaked but I also didn't have any problems with my milk when she was born. I guess I got lucky.
As far as storing the milk, in a self-contained freezer unit of a refrigerator the milk will spoil between 3-4 months. But if you have a separate deep freeze with a constant temperature of 0 degrees F, then your milk can stay in there for 6 months or longer.
I'm not sure if you know this or not but stimulation of the aerola can bring on early contractions and possibly early labor. So your doctor would probably not agree with you pumping but then again, all doctor's are different. I asked mine if I could start pumping about a month prior to my due date and he said he didn't think it was a good idea.
Oh and if you leak, use breast pads. I hate them but they work.
Hope this helps!