Whats the shortest length of true foster time- not respite?

hi i have a son in foster he went in in sept. its now nov. this week i start partial unsupervised then got o unsupervised then longer day and then nights then a weekend then a week.. everyone says my case is moving so fast because its been three months and im basically unsupervised so i am guessing this will be a 6 mo thing but in 6 mo i also have my unborn baby and i think they are holding off to see if the father pops up at birth. as he is the real reason i lost my kid due to his drugs and a ual allegation made by my 4 year old. this man is not in my life and i have restraining orders against him so im not worried but the system seems to be. what do you guys think and whats the shortest time you know of?