Nope, definately not too early.
Mine goes down at 6 pm on normal nights, and sleeps through until 6 am (sometimes later) the next morning. This is perfectly normal, and can actually be better for your lo. Earlier bedtimes often result in less night waking because they are getting a deeper, more restful sleep on the pm side of the night, and are more relaxed for the am side, allowing them to sleep through. It also sets up naps pretty nicely. But obviously that isn't always the case. If your lo prefers the early bedtime, enjoy the evening! While it can be a pain sometimes (especially when you want to be out later with her), most of the time it allows you to spend some time doing what you want, and she wakes up rested and happy. A lot of moms are early to bed advocates...I'm one of them
On the flip side though, it means that her day begins at 6 am (occasionally later, depending on how tired she is). Often this can't be helped...if your lo's biological clock gets her up at 6 am, it's not easy to change it, but it's possible with some work. You could try putting her to bed between 6:30 and 7 and try soothing in the am, but that doesn't always work, unfortunately. We just had to bite the bullet and get up with the sun. Remember you're working toward 11-12 hour nights, sleeping straight through. Early bedtimes often help with this, but I would base it on whatever time your lo normally wakes in the am.
Hope something in here helps!
*HUGS*
Sonya =P