Hi,
i did run some column with small size, typically 10cm long (i never go above 30 cm also). this was for very polar compound (eluting with pure ethyl acetate...) and mostly apolar impurities. i washed off yhte impurities first, then eluted my compound.
this is the way i always go for very well separated compounds, even if i go back more and more to longer column (i feel the compound is cleaner, don't know why...)