However, Youlden suggested he could fill one of them before October's Repco Bathurst 1000.
"I think I'll be there this year, I think I'll be there with you," Youlden told co-host and active co-driver Tony D'Alberto on the latest Parked Up podcast episode.
"I'm not in a position to make that announcement yet, but there's been lots of interest."
Youlden's absence in 2020 came in a season in which Bathurst was the only endurance event on the calendar amid the COVID-19 pandemic.
Critically for Youlden, he can stay match-fit for a Bathurst return having secured a full-time drive in this year's Porsche Carrera Cup Australia series.
"I think if I wasn't racing Carrera Cup this year, I'm not sure I would have had probably the same interest from teams leading into Bathurst," he explained.
"It is important to be doing miles... I think that's what let me down in 2019 is the fact that it had been 10 years for me just basically getting off the couch.
"I thought I did a reasonable job not doing much racing for the last 10 years and then just rocking up and doing the grand finale if you like."
He suggested teams are looking to sign experienced co-drivers, such as former Bathurst podium finishers Steve Owen and Dean Canto, with one enduro on the calendar.
"I think the other reason is that you get a lot of young guys, you talk about [Erebus full-time recruits] Will Brown and Brodie Kostecki, these sort of guys are moving up," he said.
"It's quite a unique timeframe for experienced guys like myself I guess.
"Steve Owen is another one, I'm thinking of off the top of my head, these sort of guys have done a lot [of Bathurst 1000s]. Maybe even Canto, I'm not sure what he's up to.
"Again, it puts us in a pretty strong position to come back I think.
"I did say I retired from Supercars, but again, COVID has changed a lot. The fact that it's one race, lots of things have changed I guess in two years."
The only enduro of 2021, the Repco Bathurst 1000, will take place across October 7-10.
Sign up to the Repco Supercars Championship Newsletter
We use cookies to ensure that we give you the best experience on our website. If you continue to use this site we will assume that you are happy with it.Ok