It sounds really strange, that you end up with the problems you described given your usage.
My systems are heavily modified/tweaked, so one would expect I would experience the problems you describe.
Given your usage, using an immutable distro sounds like a no-brainer to me, immutable Linux was created with your usage scenarios in mind.
In your shoes I would still try to pin point the root cause of the error, because in theory™ your usage should not be a problem for any of the mainstream Linux distros and we don’t know if an immutable distro solves your trouble.
Given your 6 montish circle it sounds like some kind of accumulation? If the computer runs stable for several month, IMHO you can rule out hardware problems, unless you have a kernel update every 6 months… :-P
Can you be more specific about your hardware, laptop model and Ubuntu version you are using?
If you ever figure out what happened, or if you try out an immutable distro and it runs for a year for you, give us an update! :-)