Good question but this question is a mind spam! Don't click on it by trying to judge your meditation or you will loose everything! Assessing the quality of our meditation is the most efficient way.... to quit; more than 80% of beginners do so after few weeks!
Meditation is simple but quite demanding and very difficult. (I’m judging :))
Controlling thoughts has nothing to do with their number -they always appear- but how you become aware of them in a mindful way*. Once you are mindful to them and only then you can deleting them and go back to your anchor of choice. Focusing on your anchor or focusing on your incoming thoughts before going back to the anchor are BOTH mind control practice.
So: you assess your meditation not on its quality per se - always never good enough - but on its impacts on the quality of your day-to-day life that is, for example, how you react emotionally to someone, something, your own feelings and you are mindful to what you are doing, where you are, etc.
How long it takes?
Practice make perfect and its effects are cumulative. May take weeks, months, years, decades, centuries, light years.... maybe in your next life. Can you wait?
Conclusion: Just do it regularly and patiently.
* Mindful way: To contemplate w/o analytic, discriminating and judgmental thinking.
Vlad Stulikov one of our Oakville Zen member emailed the following: Thank you Vlad.
1) There are no "good" or "bad" meditations. They are all "good" because they work even if you managed to keep concentration for seconds only. It often takes time to notice the effects of meditation in everyday life but meditations are sure to change you regardless your judgment and thoughts about the quality of it.
2) Even "bad" meditations have a cumulative effect. It is similar to the job: you go to work every day but you are not paid every day. Your salary is going to be at the end of the month. But to stop going to work every day because of that is stupid. Keep going and you are sure to get you salary.
3) Most people think that the mind is being trained while it stays focused on the "anchor" only. And therefore if they did not manage to concentrate on the breathing most of the meditation time then the session is "bad" and useless. That is a total misconception. The truth is that your mind is being trained at the very moment when you notice that you are not focused anymore and return the focus to breathing. The very moment of noticing is that makes you mind more mindful and skillful.