Portable Phone chargers/spare batteries

Ok all you geeks.I have my very wonderful Samsung Galaxy S3 now and splendid it is too.The thing is .. you all know what's coming next.Battery life is not so great.So since I am scared of taking the back off to change battery once a day as it's a bit flimsy I wondered about getting one of these dooberies
http://www.ebay.com/itm/220935629537?ru=http%3A%2F%2Fwww.ebay.com%2Fsch%2Fi.html%3F_from%3DR40%26_sacat%3D0%26_nkw%3D220935629537%26_rdc%3D1#ht_2607wt_1399
also figures here in our very wonderful taobabo store
http://s.taobao.com/search?q=anker+astro&keyword=&commend=all&ssid=s5-e&search_type=item&atype=&tracelog=&sourceId=tb.index&rt=1378548600087&source=haiwaigou&pid=mm_14507416_2297358_8935934&unid=
Do any of you clever people have experience of this? and should I buy the taobao one or will it be a fake? Cheers. 

Don't be worried at all about taking the back off the phone. My i9300 used to lock up very frequently and the only way to reboot it would be to pull the battery...and hope. Since I switched to a custom ROM I have not had it lock up once but that's another story.

You can try apps like Greenify to increase battery life. If you are want to get real geeky you can flash your ROM to something suited towards conservative power consumption.

There is always the chance that what you buy on Taobao is fake. Be sure you pay through Alipay (I think....my wife handles this stuff not me). The seller won't get the money until you confirm the product is in good working order and is what you paid for.