My original ASUS battery was junk less than a year after I bought the Nexus 7. Does anyone know about any of the following...

1. I'm told that ASUS brand batteries for the Nexus 7 have not been made for quite a while, so any bought now would be old stock. Is this correct?

2. A lot of the new unbranded (or non-ASUS brand) batteries I see listed for sale are 4270mAh, whereas the original was 4325mAh. Are they okay to use, or is it better to find an ASUS brand 4325mAh battery?

Geoff