In practice, this means that the PCs get minutes to survive a long swim underwater (if they are ready for it, and dive in of their own volition), or to escape a chamber that is slowly filling with gas (assuming they detect the gas before it overtakes the oxygen in the room), or if they're trying to avoid breathing in hallucinatory spores of some kind of mushroom (if they identify the fungus as harmful).
By contrast, they only get rounds to survive if they suddenly fall through a pit trap into a fully-submerged underground river tunnel, or to escape a chamber that is already mostly filled with gas (and they didn't realize it until they start choking), or if they are getting suffocated by any kind of monster attack.
Regardless of the situation above, I would never allow a minute's worth of breath-holding in a combat situation, even if the PC was fully prepared and "holding their breath" before it starts. I can, personally, hold my breath for a minute without problems... sitting at my desk or standing still. If I'm fighting for my life with sword-and-board, carrying 60 pounds of armor, ducking-and-weaving 10 meters every 6 seconds while also accurate striking and dodging, and taking solid wounding strikes in return... I'm not holding my breath for 60 seconds. I'd be surprised if I could do that for 15 seconds.
If nothing else, I'd expect to gasp on taking a hit from an enemy, or find my combat effectiveness diminished in some way. Conan the Barbarian, Bruce Lee and any number of tennis players always scream loudly when they make their "attacks". Breathing is an important part of any strenuous athletic activity, and I doubt combat is any different. If a player absolutely insisted they were holding their breath in a fight, regardless of consequences, I might allow them to last a minute or so... and be attacking at disadvantage for the entire period to represent the distraction of trying to limit their exertion.
