Alisia - From what I understand in the right environment ... ie. good cm etc... sperm can live for around 5 days. I believe once they get past the cervix (which they would with iui) and head up to the egg the just sort of hibernate till the egg is released and it sends out a beacon and wakes them up and they swim for the egg.. That is why they try to get the sperm waiting just before O so they are ready...
Does that make sense?
Oh, and I dont know if it is different for frozen sperm than fresh sperm either but I would assume it is the same...
for success for you!!!
xo