Almost doubles the battery life of the GoPro camera, how can you go wrong?

What's wrong with another 700mA versus a stock GoPro Hero3+ Silver edition battery? There's very little downside, in fact NO downside, to going with a bigger battery that still fits in the stock battery bay in the GoPro. The cost of the batteries on eBay is trivial enough to encourage even the most spendthrift adventurer to drop the coin for a bigger battery. I bought two. Why not?