I learned a lot in the six months or so (of the job I have in mind), but it very quickly plateaued and from then on it was all very much self-directed learning,

I learned a lot in the six months or so (of the job I have in mind), but it very quickly plateaued and from then on it was all very much self-directed learning, automating as much of my work as possible and writing tools to make my life easier and to learn new technologies. But there's only so much of that you can do without sufficient external challenges. Most colleagues did nothing of the sort and were roughly as productive without developing any broader skills, as far as any performance evaluations showed. It's spending an hour performing repetitive manual changes to some code, or spending 55 minutes doing it programatically in Vim and gaining some precious Vim-fu in the process. The output is the same at the end but the programmer isn't. When there is no further scope to learn from my work (apart from pipe dream re-write projects that never materialise) and I am not doing any significant critical or analytical thinking, I leave. It sounds like your place had a lot more to teach you.