This may come as a shock to most of you: to develop your astral senses, you actually got to WORK. ON. THEM.
You may do endless working and meditation but, without giving them a vehicle for manifestation, they'll always stay abstract. It's like you want a muscle to grow stronger. You feed it properly but you never use it. How do you suppose your muscle grows stronger? Through energy only?
Look to the Spiritual Warfare Training Programme: there are exercises that actually work on your hearing. They should even be on the first month. Practice those too and your astral senses will start developing.
The Clergy didn't put them there for show. They put them there because they are useful, they work. So people should start using them and stop looking for non-existing shortcuts in incremental repetition of words of power, as those only cover one part of the equation.