Lucid Dreaming | How long should it take to establish a habit like this?

So I've been trying to develop a habit of reality checking to going in and out of buildings. So far I've kept it up for 4 months and don't often forget to do it, however, it is still not noticeable in dreams. Should it take longer than this?

Also, this is just a general "cue" I've chosen, but I wonder if people have the same habit-building difficulty when it comes to more personal dream signs as well.

via Lucid Dreaming - Dream Views - Attaining Lucidity http://ift.tt/2cQA3Oe