One thing in mind with lead acid batteries is using a desulfinator. Part of the battery process creates sulfur on the battery plates. This is what typically shortens the battery's lifespan. The desulfinator injects a signal into the battery and slowly breaks down the built-up sulfur.

I've never seen a solar powered unit but I've also never looked.

There are commercial models but this is the one I built for my aircraft batteries (and also use on my car batteries):

http://www.barkeraircraft.com/eaa79parts.html

More info on desulfating and how to build the board:

http://www.barkeraircraft.com/files/Pulse3_web_layout_.pdf