Some studies show strong sperm lasting 5 - 7 days, but usually 48 hours. No way would a sperm last 28 days. Unless it was mutant =)
aif the sperm cell doesnt reach the egg within 48 nhours they die in a sense because sperm can only live for 48 hours outside the body
HEALTHY SPERM CAN LIVE UPTO 5DAYS.
HOPE THIS HELPS