I get about a smidgeon over 3 hours with thte 10w, which is perfect, because my commute one way is 90mins, so it starts going dead just about the time I get home from work.
I get a good 90+ mins on the full 16w. I rarely need that much, unless it is super rainy and foggy, and even then I can get by easily on the 10w. I usually just use the full 16w on my way home to drain the battery down to cycle and prep it for charging. I normally don't do this though.
I have been thinking of getting a smart deep cycle charger for it. Then I can plug it in and forget it.