No plugins on any tracks when recording a long session. Plugin bypass - mode does not help there needs to be no plugins
Edit / Preferences / Appearance / Editor / Show waveforms while recording = off
Periods = 3, Buffers = 1024
If you’re on Linux stay away from Calf - plugins, they will mess your session eventually. I use Ardour 5.12 on Linux and it almost never crashes (happens maybe 2 - 3 times a year).
@mhartzel 's advice is right on. With that said, my computer isn’t the highest spec-ed (old old i5, 8 gb rams) and I haven’t had a crash in a minute. I am on Linux, but I do know with Windows there’s quite a bit of tweaking in order to get something close to low-latency.
OP doesn’t mention low latency. If you need to process sound live then the best solution is to buy hardware that does the job. Imho going for low latency on a computer is asking for trouble. A computer will never give you the reliability dedicated hardware does. Low latency on a computer may work for a while and when you are depending on it it does not. I play guitar so my live processor is a Line 6 guitar processor and never had trouble with it.
As a starting point for getting stable recording my recommendation is Periods = 3, Buffers = 1024. This should work even on a slower computer.
periods = 3 is only for use with some USB interfaces, and should only be tried after periods = 2 has failed. These settings are also only for when using JACK - the ALSA backend (which we recommend for people who do not need JACK) gives you no option over the number of periods.