10 percent is reasonable any higher and you have a problem. If it reduces every year then you have an even better control over the price too. I personally think over time it should get towards 2% or 1 percent so that the POS mechanism still works.
agreed. I have seen dozens of coins like B3Coin EMBERCOIN etc... which has astronomically High PoS just crash and burn as soon as no new investors join them. 10% is reasonable enough to sustain this coins steady growth.
Coins with high inflation are doomed on failure. It is impossible to keep stable price. Only way to keep the price is to burn them on usage. But then, nobody would use them.