Describe your wood supply. Are you using hardwood logs from a supplier
or scrap timber? What size are the logs?

10KW is a fairly substantial stove, I let mine (a jotul f600) burn
freely so that it burns cleanly - I tried throttling the air supply at
night but it just started sooting up. But I have a very large space to
heat, so I'd usually want it burning at a reasonably fast rate.

It is just about possible to get it to stay in overnight by putting in
very large logs once the firebed is plenty hot but quite small - but I
rarely bother - I let it burn out.

Again once a hot firebed is established, no problem with running it
slowly and around a quarter-full, but on full air - just requires to
be fed regularly a few bits at a time - or a very few large pieces.