At what age is it ok to let them play upstairs on they're own?

[Marne]

Thats it realy.

DD1 wants to play upstairs in her room (she's 2.8)

Remove marbles and place shampoo etc on high shelf.

yes definately make sure you move stuff like shampoo, I forgot I had a large bottle of baby lotion on the side when I went upstairs dd1 had 'washed' her hair with it her dd2 hair and the floor what a mess but the room smelt lovely for ages

DS1 (3) and DS2 (20mths) - would probably kill each other at the moment if they were left alone upstairs!