I opened mine as soon as they had leaves and all are doing very well ..the foliar feeding really speeds them up...I will post some pictures when I have time to load them to photobucket

I don't keep mine tightly enclosed. I only put a lid on for the first couple of months to protect them from rain damage. Once they feel hard enough to withstand a good rain I take the lids off.

when you start to water properly and fertalise and how much of what sort.

I'm keeping my seedlings under a covered porch out of the wind, sun and rain. So I'm able to take the tops off after a few weeks not months. However, I'm having to water them at least two or three times a week. I usually do a container dunk about every 2 weeks and just do a top mist or careful top pour the rest of the time. I only put a little water soluble fertilizer in the mister every two weeks. I guess that since they don't have cups to hold water they are going to dry out fast if I'm not careful. So far they look good and have survived the winter.