The Grow Must Grow

Successfully germinated all 3 of my seeds under my bed using paper towel method and grew beautiful, long taproots. I planted them about 1/4 inch down, making a tiny hole for the taproot. For all 3, I awoke the following day to find they'd all sprouted. I've got 3 seedlings going - the most I've ever planted successfully & I'm hopeful I can actually do this!! I've moved the light down to about 6 inches, making sure it's not too hot (my TS600 doesn't seem to get hot; I held my hand directly above the plant for over a min to make sure), as I want to avoid "stretching." I have plastic ziplock bags with multiple ventilation holes cut throughout (to keep humidity down, otherwise it's over 90%; the holey bags keep it at a solid 77% or thereabouts), and I make a point to check them at least 3x daily to make sure the soil stays moist and remove them during the period the light’s off - from midnight to 6am. The question now is, how much bigger should my plants before I can remove the bags permanently? Technically, it’s still a seedling, and I’m not sure how much longer to use it. For the moment, the plants look beautiful and it seems not to be bothering them. Any advice for me?