TechnologyOne chief executive Adrian Di Marco has been one of the longest-serving leaders of an ASX-listed company, but on May 23 his time at the helm of one of the country's most successful tech companies will come to an end.

In an era where the average tenure of a CEO of an ASX 200 company is only five years, Di Marco has spent 30 years in the top job, but he still remembers the penetrating smells of the tannery in Hemmant, Brisbane, where his company was born in 1987.