I am a fan of slider phones so propel pro (3 years old) is still my basic phone. I bought several batteries claimed 2500mAh for my i627, While these mpj only being several hundred mAh larger than my stock battery, but I'm seeing close to 35% longer battery life. Great choice for replacement. Not cheapo Ebay batteries that last a week then dies.
I think using two batteries on my mobile to avoid having to be constantly plugging it in might prolong its life? At least my phone works perfectly.