Which direction should the valve be left in?

Still with my Vokera 20/80 Combi. boiler... I'm currently bleeding the radiator (already filled one bucket of water). Now I can't remember which way the 'top-up' tap should be left: straight up - so it cannot turn any further anti-clockwise or horizontal?
Also how long is the bleeding likely to continue? (I'm going out in four hours!)
Many thanks!