Mattias, since it’s your subconscious, do whatever makes you feel like you’re getting the point accross. Personally, whenever I perform a reality check or think about dreaming in general, I remind myself that I am a lucid dreamer. Additionally, as you mentioned, I repeat my mantra either until I fall asleep or for about two to five minutes if it’s keeping me up (which is the MILD technique).
As for asking too much: no, you can’t reach any limit. Like I said, your subconscious wants to do everything it’s commanded to do to satisfy you. Now, if you’re giving it paragraphs of information, I do think you could confuse both your conscious and subconscious mind due to the inability to concentrate and process everything at once. Keep your sentences short and simple–no need to add in fluff.
In the end, just make sure you do what you feel will work most effectively.