A mantra is supposed to be singular, but having some self affirmations is good. Self affirmation is good foreground and background. Your mantra is kind of supposed to always be a background idea. I have done something similar with my mantra (I'm dreaming) and found that if I did this, I would come up with the words in my dream, since one of the main points of LDing is not only awareness in itself, but awareness of the dream state, so if that word comes up, it is a good thing. All around, I would say it is a good supplement practice, but would need a good sleep schedule and night work to work.

People act like habits are a bad thing. You need habits to ld. There are good and bad habits. People act also like something in the background won't work very well, but you can't keep dreaming in the foreground all the time, but for a lot of techniques, the goal is to move something from consciously doing it, to unconsciously doing it.