I bought one of the 22400mAh powerpacks as an upgrade for a Tecknet 9000mAh power pack. This has almost two-and-a-half times the capacity but at the price of a bigger and heavier package (448g vs 248g). The power-to-weight ratio is better than the TeckNet, but even so it's probably worth considering whether you could get by with a smaller and lighter pack.
Plus points, apart from the capacity, are that it has two outlets (one 2.1A and one 1.1A) and you don't need a dedicated charger. It seems to be a neat well-made and solid package. I can't comment on the long-term life.