Here's some links and there is one in that thread that leads to more:
http://www.toyota-4runner.org/4th-gen-t4rs/62199-panasonic-battery.html
http://www.toyota-4runner.org/general-discussions/39626-06-battery.html
Use a large Philips head to unscrew the six caps. Add distilled water only. Screw the caps back in. Eazy.
Here's my take on it...
Do you buy a replacement tire when you have one that's low on air? No. You add air, which is doing maintenance.
Although the battery says maintenance free it's not. Do maintenance (add water) and it will last. Not sure about others but heat is the enemy to this battery because the water evaporates. I'm guessing that so many are replaced in the south because they aren't maintained and then they prematurely fail.
Your's hasn't failed yet. Why spend money on something to replace what is one of the best batteries I've seen.
Not sure what the alternator amp output is but I was able to resurrect mine years ago and it's still strong, even now up in the cold north. Putting it on a trickle charger will no doubt help.
As many others around here feel, getting to know and working on your T4R is priceless. I didn't know about the battery until I had the same issue as you. I learned from this forum and it saved me $$$ on lots of items.
If this were a poll, my vote is Save The Battery!