My battery hasn't given any problems, but it was close to that 5 year window, so I decided to replace it with an upgraded AGM type battery from Odyssey. It has very similar ratings to factory battery, but has a slightly longer reserved time and more amps, but is also in a much smaller package, built to military specs, and charges many times faster than regular lead acid battery. The great part is that this greatly upgraded battery was only $220 at my local Battery World store (part number PC1200)

The battery is slightly smaller, even though it is more powerful and charges faster. To secure new battery, I just added a little piece of PVC molding to make same length as factory and added a little strap to hold down since it doesn't have a lip sticking out of bottom to hold down like factory. There are many ways to secure battery into the battery tray, but I added a detail explanation of what I did in case anyone was curious. On a side note, the other battery uses part # PC-1350 which is exact same size as factory battery. The batteries in car are Group 47 and 49 size.

Detailed explanation of how I strapped down battery:
Since the battery is shorter in length by 1.5", I had a piece of flat board I stuck on to side of battery with double stick tape to make it same length without adding much weight and making it easier to install. The left side of battery tray has two holes for the tall tie downs that are the metal rods with hook at bottom and threaded top. I decided to use a motorcycle strap to hold battery down, so I cut off connector off strap leaving a sewn in loop on the left side of strap. I used two heavy duty tie straps through loop and two holes of battery tray to secure left side of strap. The right side has a bar that holds battery in place at bottom edge that I secured right side of strap to and tied off for now. I am going to get a standard buckle so I can thread right side of strap through for cleaner look and easy removal if necessary as opposed to a knot tied.

Basically the factory battery had a little lip a bottom edge to hold down battery, but the Odyssey battery is perfectly square, so that is why I added the strap, although with the space I added, it is same length and width and can't move in battery tray in any lateral direction. The strap will hold it down if I ever jump a ramp somewhere, so that's why I added the strap, although the weight of battery and wires connecting it won't let it go anywhere regardless. As a little overkill, I put down two strips of double stick tape on bottom of battery tray to stick battery in place, so it isn't going anywhere even without strap I added.

Here are pics:

 

Nice! Have used Enersys batteries in the Ferrari and other vehicles. They are great batteries and thanks for the writeup!

 

Very nicely done with money in the bank from savings made!