Thanks for all the input guys. Jordan - that's some great info about the charging/maintenance. Talk about a PITA, but that's likely what caused this thing to die so soon. To be fair, it's not "dead," but I'm pretty sure it's getting there, and I don't want to risk it going out on me during a trip. We're getting into colder weather soon, which is when these kinds of problems like to rear their ugly heads at the worst possible times. I don't have a load tester, but I did a simple voltage test. If you guys remember, I'm actually running two batteries. The Odyssey under the hood is my primary/starting battery, and I have an Optima Yellow Top under the driver seat that acts as an aux battery (it is isolated from the main circuit of the vehicle when the ignition is off). With the rig only having sat for about 10 hours (after a good bit of driving), the Odyssey was only testing at 11.3 volts, and the Optima was testing at 12.6 volts. Seems that the Optima is fine, but the Odyssey isn't. If I let the truck sit for 3 or 4 days, it turns over really slowly. I haven't tested the Odyssey's voltage in that condition yet, but I'd guess it's down into the high 10V range if it's turning over that slowly. To be fair, my alternator is also 7 years old now, and is likely strained from charging two batteries all the time. I'm probably in the market for a replacement in that department, too.
I called 4 Wheel Parts and was told the Odyssey battery only had a 1 year warranty (they looked up my receipt I bought it just over 2 years ago), but I found the same 48 month info online that you guys are saying. Maybe that's just how long they take care of it in store, and I should call Odyssey directly. If they'll replace it for free or even prorate it, I guess I'll just go with another one. If not, I think I'll swing by my local Batteries + and pick up the 27F that knightrider is running.
Edit: I found this info on Odyssey's own warranty card. With this kind of verbiage, I can bet any kind of warranty replacement is going to be a pain, especially if 4 wheel parts isn't going to work with me on it. I should probably just anticipate buying something new.
Overcharging, undercharging, charging or installing in reverse polarity, improper maintenance, allowing the Battery to be deeply
discharged via a parasitic load or mishandling of the Battery such as but not limited to using the terminals for lifting or carrying the
Battery. Trickle chargers that do not have a regulated trickle charge voltage between 13.5V and 13.8V (no lower than 13.5V and no
higher than 13.8V) will cause early failure of the Battery. Use of such chargers with the Battery will also void the Battery’s warranty.
For applications where an alternator is present, the alternator must deliver between 14.0V and 14.7V when measured at the
Battery’s terminals. Consult the ODYSSEY battery technical manual or owner’s manual for any necessary temperature
compensation. Alternators that do not have a regulated charge between 14.0V and 14.7V (no lower than 14.0V and no higher than
14.7V) will cause early failure of the Battery. Use of such alternators with the Battery will also void the Battery’s warranty.