First and foremost, sperms are released within the seminal fluid which needs to be in the right volume (1.5 to 5 mL) and pH (7.05-7.8) and contain optimal nutrients (fructose), enzymes, proteins and other substances necessary for survival of sperms.
If released within the body of a female, sperms can stay alive for up to 3 – 5 days. This means that if released before a woman ovulates, the sperms can still fertilize the ova if ovulation occurs up to 5 days from the time of intercourse.
If sperms are released in other environments e.g. on a dry surface, their survival period is shorter.