Best replacement battery for 3g?

[Effenpig!]

According to my serial # I have an '08 week 33 iphone 3g. Does this sound right? Anyway, I think the battery is getting a little "tired". So my questions are:

1. Is there an average "lifespan" for the battery under normal use?

2. What is the best replacement battery?

3. Source for said battery?

I don't want to tear down my phone just to install some knock-off el crappo battery. ALso, I'm not entirely convinced that some of the parts that are sold as "OEM" are legit.

TIA

[lewkskywalker]

I am also wondering if you can squeeze a 1600 mah in the iPhone 3G. Any ideas?

Thanks!

[flyboy320]

A bump and a subscribed....I have to replace mine as well.