Pretty amazing battery.  Back in June 2009, I purchased an Odyssey PC925 battery to put into a 91 K75S I was selling.  I bought the bike back last July and let it sit since then.  Over the weekend I pulled the bike out to bring it back to life and was somewhat surprised to see a running clock.  Just for kicks, I hit the start button and the bike turned over pretty well.  I then checked it with a voltmeter and it read 11.2V - from a nine year old battery that had sat untouched running a clock for 10 months!  (I don't know what it's state of charge was when I got the bike last summer.)

While I was redoing the bike's fuel system I hooked it up to a Battery Tender Jr which brought it back up to 12.5V and, once I had the bike sorted out, it had no problem starting the bike.

I wasn't 100% sure if it was the same battery that I'd installed in 2009 but when I pulled it out to do a spline lube it had the installation date of 6/09 written on it my handwriting so it is the same battery.

I've had a similar experience with the 680 model.  I'd add that this is not my blanket endorsement of the Odyssey battery line in general.  I've had them died after 3 years as well.  Buying batteries has always been something of a crap shoot for me.

I've seen some other reports of them going bad too so you're not alone. I've had about 6 or 7 of them and have gotten good life out of all of them. (fingers crossed)

I hear varied reports on the Odessey batteries but more often it's good. I had a really good run from the first Motobatt I used but not so good since then.

I've got an Odyssey PC680 in my garage that has ten years of use on it. I got it from the warranty pile at work five or six years ago - it had a swollen case which subsided after a short while. I continue to use it for airing up my tires with a 12V air pump and lighting a 12V shop lamp. It rarely requires a freshening charge - when it drops to 12.4 volts or so - maybe twice a year, and never charges for more than fifteen minutes. 

The Odyssey rep at a moto-related tech show told the crowd to never use a low-amp maintenance-type trickle charger on them over the long-term and to hit them amps (6, 10 or even 50A in half hour bursts) if they drop to a low voltage number. That was in 2003 or '04. I don't know how much they've changed internally since then.