I have to stay off marijuana for at least three weeks to even have a lucid dream that lasts more than a few seconds. It takes about seven weeks to start having good ones. But you need to consider the fact that when I smoke, I do it every day, all day when I can. I don't know what effect smoking once a week would have. I haven't managed to pull off that schedule yet. Marijuana is definitely not helpful at all with lucid dreaming.