My plant is in a 9cm pot, and I know I grow my plants quite "hard". But I lost, I reckon, aboit 3-4 years of growing time after my heating disaster in 2000. Everything that survived seemed to stand still for a long while, and its only these last 3 years that everything has been growing more normally.
I don't think I have changed much else, perhaps apart from my compost, as it was about 4 years ago that I discovered a source of grit that seems to work better than the stuff I used to use. It might be that, it could be many things - better winter temperature controls...