Well I have 5 of my plants out and they been out for about a week now. Still have 4 more I started about a week ago and don't plan on taking out for another 2-3 weeks. I agree about not taking out so soon but where I live frost in May is extrememly rare, especially into the second week of May.
The plants I have out now are about a month old. Three weeks indoors and a week out the woods. So I dunno if you would still consider them seedlings.
The weather service is saying a low of 29 in certain areas, with 3 to 6 hours of sub-freezing temps. I'm thinking about going out and covering them this evening. Not sure what to use but I heard newspaper works ok. The only thing is I don't know what time I can get back out there tomorrow morning to take it off. It might not be til 9am or 10am until I can make it back out there. Plus this wind is crazy, but I read on a gardening site that is actually a good thing since it doesn't allow for condensation, which forms the frost. They say it's not so much the cold temperature, but the actual formation of the frost crystals on the foliage is what damages it.
As for the strain, it is the Outdoor Mix from Fantaseeds, so I'm assuming they are more hearty strains, but you never know. I actually emailed them a few months ago shortly after I bought the pack and they said "Our Outdoor Mix is a random mix of seeds suitable for outdoor growing. And there is Skunk#1, Masterkush, Top44, Flashback, Caramella, Afghani. Northern Lights, in there."
I hoping they will be fine, but like someone said, not sure how well I'm going to sleep knowing how cold it is going to be.