DS is 17 months. Bedtime used to be 7, which to me is a reasonable time, but he made it pretty clear a few months ago that he needed to be in bed earlier so we moved it to 6. He immediately started sleeping deeper, waking less and being happier during the day. His napping also improved (from 20 minutes to 40+)
Now, I follow his lead - which often leads to him being in bed and asleep by around 5:15. The last 2 nights he's been in his cot at 5, shouted for a few seconds then chatted/moaned himself to sleep in under 15 minutes. He then sleeps till about midnight when he needs a nappy change (has never tolerated a dirty or overly-wet nappy, we're in cloth but I've tried disposables with no discernible effect) and on through till 7am.
It just feels so early! He naps for 1.5-2 (occasionally up to 3) hours during the day from around 11:30. So my actual "working" day with him is 9 hours long with 2 hours for lunch - that's a lot better than my t+c's when I was in paid employment 
So, wise people, please reassure me. He was a fairly poor sleeper up until 10 months when I night weaned him (bf, self-weaned at 15m) and things have gradually improved since then until we're at this point. But, really, 5pm bedtime?!?!