Should not be a problem. I move my plants out of the "greenhouse" with heating mats as soon as I see about 6-7 plants of the 9 cells in 8-09 inserts (8 breakaway sections with 9 cells each in a 1020 compatible flat. 72 cells total).
The plants need to sleep at night in any case, so they will be very used to warmer temp during the day and colder during night. 60F might not be totally optimal, but I just don't think it is going to make a whole lot of difference in the end.

it shouldn't. We don't use a heat mat at all and we start our seeds under shoplights in the basement.
Average basement temps here were about 65F and the plants did great.

kendra

This is the first year I have started seeds under lights before mid March. The (naturally) cooler temps in the house now seem to give shorter, sturdier plants. In the spring, I often end up with long, leggy, thin plants no matter how close to the lights I keep them. Seems like somewhat cooler temps (60-65) may actually be an advantage.

I just put mine in the airing cupboard and thats always around 75 farenheit. My seeds ALWAYS germinate at that temperature :) In fact my seeds are just starting to pop throught the soil just now for my plants this season.
Gonna do 20 (Trinidad Scorpion) & 20 (7 POT) and usually get 99% germination :)

Scottish arthur, what is an airing cupboard? I've seen a few references to them and am curious to know if I have one that I call by some other name.

Naturegirl, Its the cupboard where my gas boiler is kept and we in scotland keep things like towels and dry clothes in it as it always a constant 70 farenheit or just above or below 70.:) Perfect for germination as i have had 99% success germinating my seeds in there.:)

thanks for the feedback. I decided to set about half of the seedlings out in the ~60F temps and they seem to be doing fine, but with slightly slower growth. time to do the rest I suppose.

Thanks!