Does the windows wallet need to be online all the time for the staking to take place?
If your wallet is open 24 hours a day, you will earn the guaranteed annual 3%.
If you open your wallet from time to time, you can still earn Block tokens by staking but less than 3% annually.
I do not believe that this is accurate, as I receive at 3% on Block wallets which are not always open (some are on laptops that are not always turned on). I think they only need to be opened once every week or so in order to keep staking at the standard rate. The devs could say for sure about the exact time period, but I do remember Dan saying previously on Slack that this is the case.