Tom, I would check out the Garmin GPSMAP 60Cx and 60CSx, depending on whether you want the altimeter and compass. I got the CS just because I'd rather have it and not need it than....plus it's good to use the compass for bearing/heading when you're moving slow (walking).

It says 18hrs battery life, but I don't know what features are enabled with that. For example, you can disable the electronic compass and WAAS if you want longer battery life, as well as disable the backlit screen. For the record, I own the one without the expansion card slot, but have used it since about Christmas and I'm VERY happy with it so far. Only time will tell if it will be durable enough to have a long life getting beat up in a kayak in the saltwater. It's really customizable, has a easily readable screen, a simple user interface, redraws maps really fast, and so far has been durable and accurate. Good luck, there's a ton of info out there.

(This all assumes you're looking for a handheld unit)