This is an excellent question. I was going to ask it last night, but the damn computer was hiding from me.
I'm also hardening off my plants, and it's been raining so hard every day here, I've had no choice but to leave them on my screened in back porch each morning before work so that they get filtered sunlight for about 3-4 hours. The only other times I've been able to get them out of the house on weekends it's been cloudy, so I just stick them in the "sunniest" spot I can find.
MY question was whether it is necessary to acclimate plants to a normal light cycle if they've been under 24hr light. For now, I've been bringing them inside each evening and putting them back under the lights. However, they're in a room with a ceiling fan blowing all day too, and all the windows are opened to let in cool night air, so they're pretty much used to the temps.
Should I just begin leaving them outside all the time in a protected place if they can handle it, and then just begin to slowly build in sunlight exposure?