Eh, my main usage right now is my Photos library, which is currently at 930gb. I like to keep originals on my main machine so that everything gets backed up to my NAS with TimeMachine as well as being in the cloud. With pets and young kids, I end up with quite a lot of photos and videos. I'm currently at 1.9TB used out of 2TB. The only real thing I can see needing additional storage for for the next few years is my growing Photos library but it would have to triple in size before I filled a 4TB drive.Good. I hate external disks too, even SSD’s (Sandisk are almost as fast - 2050mb/s but not even near 6000mb/s plus I hate dongles they’re not handy). Why only 4TB though? You’ll be maxed out in no time. And in a few months you’ll regret not pulling the trigger on the 8TB.
To go to 128GB RAM and an 8TB drive instead of the 64GB RAM and 4TB SSD I've gone for, it would have cost an extra £2k. 64GB has been fine in the M1 Ultra Studio that I'll be replacing and so I'd rather put that £2k towards my next machine when 4TB finally ends up being restrictive for me in a few years time.