I am re-reading my response to this, which has now changed after starting a program with these as a main component. I think @Malaka79 is pretty spot on with his advice of adding weight and practicing for perfection is better than adding reps. My initial advice was based on my experience of using these simply as a warm up rather than as a strength progression.
@LeMaqSportif - how is it going? Over the last few weeks I have been doing these daily and am up to doing reps pretty smooth with a 28 KG kettle bell. I also enjoy them and find them more like a “practice” than a workout, although clearly I’ve gotten much stronger at them.
As I’ve worked on these, I have began to see them as the “push” version of a deadlift, where you are starting under the weight rather than over it. My thoughts are that KB training in a conventional sense (focusing on swings, get ups, and snatches) won’t get you the hypertrophy you would get from traditional barbells and dumb bells, but seems to encompass all aspects of training: strength, endurance, power, and mobility. Doing smooth, deliberate get ups will demonstrate any holes in your overall movement patterns and strength, while suitably heavy swings (especially 1-arm) with only moderate rest will improve your endurance. I personally am finding daily KB work supplemented with a 10-15 minute bodyweight workout (pull ups and dips, or push ups and rows) to be very effective and a nice break from heavy barbell training.