Grubb, of Alexandra, was the sole organiser behind this year's 14th consecutive Goldrush - held from March 20 to 22 - but said work commitments were making it increasingly difficult to dedicate time to the multisport race.
He and fellow Alexandra resident Ritchie Bailey established the event "out of passion for Central Otago" in 1997, Grubb said.
Together they had organised each Goldrush, until this year's event in which Bailey was not involved.
Grubb said as his Otago Central Rail Trail-based tourism business had grown, he had less time to dedicate outside the company.
"It's a totally different situation that I've found myself in.
"At the start we had the time, so it was easier.
"Organising the Goldrush takes about one and a-half months out of my year," he said.
Goldrush competitor numbers had decreased in the past few years, but that had no bearing on the event's future, Grubb said.
"We are not struggling, the numbers are sustainable.
"Competitor numbers have gone down but that's more of a reflection of the economic climate and the variety of things on offer now.
"Multisport is not a mainstream sport and there's only a certain number of people to go around," he said.
Dougal Allan, who the Goldrush on Monday for the third year in a row, said he had initially planned not to enter this year's race.
Allan, of Wanaka, said he signed up after hearing its future was uncertain.
"I thought I better do it unless it was the last one," he said.
Allan said the Goldrush deserved more competitors in the individual field, and hoped it would continue.
The first Goldrush comprised about 175 competitors, and at its peak it had about 540.
This year 280 took part, mostly in teams of two or three.
Grubb had not made a final decision about whether to organise next year's race, and said it was more difficult to do so immediately following the weekend event's success.
"Whatever way I hope it will go ahead, but maybe with a different structure as far as the organising is concerned.
"A lot of events like this are run as businesses now, and part of the reason behind that is there's a hell of a lot involved," he said.
More than 50 volunteers helped out during this month's three-day event, and some community groups relied on the Goldrush each year for fundraising.
Clyde Primary School's Parent Teacher Association had catered part of the event for the past 10 years.
PTA member Debbie Berg, of Clyde, said about 20 volunteers and 10 year 8 pupils were involved in the annual catering, which was the association's main source of fundraising.
Year 8 pupils made money for their annual camp, and the PTA used its Goldrush funds for various things, she said.
"It would be very sad to lose it," Berg said.
