Some questions I have:
What exactly does unlocking the wallet do and what is the difference between say unlocking it after 10 days, 22 days or 35 days.. Will the interest earned still be proportional to 20% ?
What happens if I leave the wallet unlocked all the time?
The devs/community need to make it as easy as possible for everyone to know exactly what they are doing.
Let me try to help you. I have a fair amount of experience with POS minting using hobonickels (and I wrote an article about it which was well received.) The principal is the same for Mintcoin, with a few different variables and features.
Until you have coins that are at least 20 days old, there is no value (for you) in leaving you wallet open, locked or unlocked. Once you have coins that are at least 20 days old, you should leave the wallet OPEN AND UNLOCKED 24x7x365 if possible. Keep in mind your coins are going to be split up into different ages, so once you mint your first reward, you gotta keep the wallet open all the time. If you do not do that, you will not get the full amount you could have. As you mint more and more coins, they will all have different ages, so different chunks of your wallet will be attempting to mint at different times.
What happens is basically once the wallet detects coins that are at least 20 days old, it begins mining in the background using your CPU only. Your wallet is essentially competing to find the first block, just like with normal mining, only no one can hook up GPUs or ASICs or do anything to really gain an advantage, so there is no computer arms race at play.
There is a factor that gives you some kind of advantage which I do not yet fully understand, based on how old your coins are. In other words, if you are trying to POS and you have some coins that are 25 days old, and the only other person trying to mint has coins that are 20 days old, you should get yours first.
If you wallet is not unlocked, it does not attempt to do POS minting at all, so you simply won't get anything.
Does that help?