I hadn't done a pre vac at all for ten years, :

But if there was one useful tip i picked up from the recent ncca course is that your probably better off spending more time on the vac than extraction.
it gets all the dry dirt out & lifts the pile,

I do it on every job now & most comment how the last cc didn't bother (it was probably me :

)
It actually does make the cleaning easier.
Oh and the other tip was to put me prices up

regards
steve