I don't know about the long photo period. Some plants do need a dark period, but I don't know about eggplants. You can try 18 hours light, 3 hours dark; same proportion but have some rest period.

And have you considered raising the seedlings up? You don't always have to lower the fixture. A shoe box, a few books, a stack of magazines, or many other things can be used to raise the seedlings.

I have not tried doing that but I don't think that the long photo period should be of any much concern. Although when starting on seeds, you are only advised to have an 18 hours on and 3 hours off photo cycle. But if you're doing great on that set-up, there shouldn't be any worry :)