We are having discussions about raising the rate as the block chain gets longer. Minters are transaction processors. Part of the tradeoff for fast confirmation times is an elongated chain. However, a long chain puts a burden on minters who must keep an updated chain. A 5% flat APR may not be enough compensation in the long run, especially considering that the true inflation will be much lower because it may not be worth it to regular users to keep a full chain just to mint on their "spending money".
I personally think a lower rate is better. There is less money coming in needed to maintain the value. POS minting is not energy intensive, and minters can receive a good reward with even a laptop, or raspberry pi or simple computer. No special hardware needed. I think that preserves the value of all the other coins as well.
Yes. However, consider that after less than 3 months, the block chain requires nearly 250 MB, with most blocks containing no transactions outside of the mining or minting transaction of the block. What memory will be required of minters after 3 years, or 10? Additionally, there is computational overhead to search the blockchain and make calculations from the data. The compensation system will take these future needs into account.