Has there been a longer gap between gold medal wins by the same person in an individual event? If so, how long is the longest gap in Olympic history?
Sir Mark James Todd is a New Zealand horseman noted for his accomplishments in the discipline of eventing. Although he didnt win the gold medals, he holds the record for longest time between two medals and thats still really impresive
Aladár Gerevich (16 March 1910 in Jászberény – 14 May 1991 in Budapest) was a fencer from Hungary, regarded as "the greatest Olympic swordsman ever". He holds the record for the longest time between two gold medals. He won his first 1932 Los Angeles and last 1960 Rome. He does not fit your question 100% because he won multiple gold medals during that 28 year period
Birgit Fischer (born February 25, 1962) is a German kayaker, who has won eight gold medals over six different Olympic Games, first being in 1980 Moscow representing East Germany and the last one in 2004 Athens.
I believe Anthony Ervin is the only sportsman/woman who won two golds in such a long time span.