I used to deal with setting up all different featured speaker’s laptops for business luncheons with projectors for dozens or hundreds of attendees watching PowerPoint slides and so forth. I have dealt with laptops in pressure situations week in and week out for years. Think laptop roadie in a jacket and tie.
If you’re going to use a laptop and you need constant maximum CPU frequency, you have to force the “maximum performance” power profile. This has implications, The laptop will be consuming the maximum power. If you’re running it off the battery, you have lit a fuse and the fuse is going to reach its end. At that power profile you shouldn’t expect to get much more than 1-2 hours maximum before it shuts off rather than turn into a rather unexpected stage pyrotechnic.
It’s also going to get super hot for that hour especially if you have CPU hungry VSTs running (I’m looking at you 35-second IR convolution reverb). That means the fan is going to run full blast the whole time. It also means that even with that fan running all the time considering the battery resistance, ambient room temperature, heat rising up into it from an equipment rack right under it… it could STILL have a thermal shutdown, even though the battery hasn’t drained yet.
Laptop manufacturers are really picky about not accidentally acquiring an unwanted reputation as manufacturers of surprise fire bombs, so they have BIOS features to shut down whatever the OS or apps might be doing. They’re really serious about that. That’s why I would also strongly advise AGAINST overriding such features in the BIOS or UEFI. You could literally start a fire.
It may seem like overkill or silly, but it would not really be to get one of those laptop stands with the fans built in underneath. Another extreme precaution you could take would be to actually put one of those frozen athletic ice pack things under that. Every little bit of temperature reduction helps and all you have to do is get the temperature down a couple of degrees for everything to be fine.
It’s not feasible or neccessary to get the operating temperature down to room temp - that’s just not going to happen with the performance profile under battery. But getting the temperature down a couple of degrees is going to be the difference between problems and no problems.
Also consider running the laptop off AC power instead of the battery. If possible and you have an extreme temperature scenario like maybe outdoors in the summer, consider removing the battery from the laptop and running it off AC, A lot of the heat actually comes from the battery, and that actually gets hotter as it gets to its 20% shutoff point.
Another little tip if you must use the battery is if you don’t need to see the screen brightly per se, turn down its brightness. Just doing that could greatly reduce the current draw especially from a battery. LEDs are current hungry and you might have 8 or 12W of a 85W power budget just tied up blasting the screen as bright as it goes. Maybe consider rigging some sort of shading thing around the screen so you can still see it even at a lower brightness. If you can plug it into an external monitor maybe powered by AC, that could (depending on laptop GPU features) actually let you shut off the built in monitor taking a literal and significant load off the laptop battery.
If your laptop design allows removal of the battery you might actually be shocked at how much cooler it will run with the battery pack removed.
Also open up the laptop or bring it to a shop and have it fully and professionally cleaned inside and out. You would be amazed at the amount of dust etc that builds up inside. Dust, hair, schmutz of every description gets pulled in there through the fan vent and turns into an insanely and increasingly effective blanket that clings to every possible surface in there by static electricity.
You hear about people using “old laptops” for this and that. Guess what? The amount of dust insulator and blocking airflow in those things could easily reach millimeters in places over a long enough time. Imagine a down duvet that sticks on one side.
If you’re using a laptop live you probably want to have it cleaned. And you may want to replace the battery pack too, old ones get hotter sooner.