I keep my gamepad in the charging cradle when I'm not using it. That helps keep it ready for play. I do use the pro controllers more though. You heard right, they last a long time on one charge.
The gamepad is really nice for off-tv play. The other day one of my kids was playing DK Tropical Freeze on the gamepad, the other was playing DK Country on the 3DS, and I was watching recorded dvr shows on the tv. Pretty cool.
You can also buy a new battery (from Nintendo, at least. I don't remember if it's available elsewhere) that extends playtime on a charge for the gamepad. This has made a big difference in longer play sessions for me.