My truck, since I have owned it since 2013 hasn't required a drop between oil changes. I was checking weekly/bi-weekly and finally monthly after I purchased it. Now it is mainly done the next day or within a few days after an oil change just to make sure I added the correct amount.
With my wife's Impala, I have been checking at least once a month and will continue to do so until I am certain and get a good baseline to increase that.
I have never checked any oil level at a gas station as to get a proper reading, imo, the vehicle should have sat for a couple/few hours first. I always check prior to a long trip and will check, maybe, after the vehicle has sat a day or 2 or before the return trip home.