I have herd that some Japanese sperm can last for years and years.
They emerge from the hiding place back into a world changed beyond all recognition, only to discover that their mates have found eggs, grown into adults and moved on with their lives.
The last known case of such an instance was in 1978, when a sperm, considerd lost in 1939, emerged during a particularly energetic game of Twister.
The sperm is believed to have belonged to Isawa Aiyaki a Japansese Kamikaze pilot, who flew over 40 successful missions before retiring in 1945.
Trust this helps.