Battery Replacement Program

My first iPod, an 80GB iPod video is nearly four years old now and is only getting 8-10 hours of battery life. Half of what it originally had. Even though I'll get a touch sometime soon, I don't want to let go of this one, especially because they no longer come in white.

My question regards the battery replacement program. If I take it to an Apple Store in Canada it's $70, but I want to know if they'll replace it with the 20 hour battery it originally came with or the 36/40 hour battery the next 80GB came with. Ideally, I'd like the most bang for the buck and the site doesn't specify. You can buy the 40 hour batteries for pretty cheap and it doesn't seem too hard to replace it yourself. Anyone had experience with Apple's replacement program for older iPods? They still offer replacements for the original iPod, surely they don't even make those batteries anymore (?) so I don't see why they couldn't put something newer in it.