Australia will make at least one change for the Boxing Day Test against India, with Scott Boland expected to come into the side for the injured Josh Hazlewood.
After Hazlewood strained his calf on the morning of day four in Brisbane, Marsh was still only used for two overs as Cummins and Starc did the bulk of the work.
Australia's team staff put that largely down to weather delays keeping the two front-liners fresh, as they bowled 48.1 of the 80 overs India faced in the drawn Test.
With Hazlewood injured, the duo's fitness now looms as crucial for Australia in the final two Tests with the series level at 1-1 and India one win away from retaining the Border-Gavaskar Trophy.
But Cummins said he and Starc should have no issue playing through the summer unchanged, featuring in all five Tests.
"Nothing is for certain, we'll see how we pull up. But today we're fine and I can't imagine that changing," Cummins said.
"We're feeling really good, it was hot (Tuesday) but we'd had about seven days or so off bowling after Adelaide so we were fresh and ready to go.
"If anything, the rain breaks actually helped us get a bit of a break."
Starc and Cummins have now bowled 90 overs each for the summer, while Marsh has contributed 23 as an allrounder.
The West Australian had battled back soreness early in the summer, prompting Beau Webster to be called into the Test squad as cover.
But Marsh indicated he was now clear of that in the lead up to the Gabba.
Mitch Marsh is expected to play a bigger role with the ball in the Melbourne and Sydney Tests. (Dean Lewins/AAP PHOTOS)
Cummins said the limited use of Marsh had nothing to do with his bowling ability or fitness, but was more tactical in case he was needed in the fourth innings.
"It was a bit of an eye to the second innings, with a fresh new ball, we would have leant on Mitchy a lot to try and take those 10 wickets," Cummins said.
"It's always a bonus having the allrounders.
"I suspect we will call on Mitchy enough in the next few Tests to get us a breakthrough or two when we need it."
Cummins also said he felt for Hazlewood, who has now picked up two injuries this summer after missing Adelaide with a side strain.
The 33-year-old endured a difficult run where he played just three Tests between the end of January 2021 and start of June 2023.
"He's probably one of the most disciplined professional sports people you'll ever meet," Cummins said.
"I don't know when he will be able to go again. But I think you've seen this series how much we rate him and how much of an impact he can have."