The annual income from staking is roughly 1.5% – 2% of what you are staking if you stake 24/7. There is a staking calculator here, but it gives slightly low average estimates. Any estimate of the time it takes to stake successfully is an average estimate. If you are expecting to stake 1 STRAT every 10 days, you may have times when you stake twice a week, and you may have times when you stake once a month. On average, it should come to 1.5% a year when staking 24/7.
The full calculation for the annual staking income is as follows:
Annual income (%) = 100 * (Number of newly minted STRAT per year) / (number of STRAT staking)
Number of minted STRAT per year = number of new blocks per year = (seconds in a year) / (block time in seconds) = 31,557,600 / 64 = 493,087.5
Number of STRAT staking can be found here. At time of writing is around 27,000,000 STRAT
Thus, annual income (%) = 100 * 493,087.5 / 27,000,000 ~= 1.8%