It all depends on your starting point. If you start out looking like David Beckham, there's never going to be a point (maybe short of FFS) that you can't pass as male, especially, as you say, if one is trying to.
For me, personally, I would have a hard time passing as male now after a year of HRT. But, it depends; for example, 3 months ago I got "sirred" after having electrolysis (my face being red/bumpy on the beard area). And then, a week later, the same teller "missed" me without makeup but no electrolysis redness either. So, things can change depending on perception, even with the same person.
Lia