I don't quite understand your question, so I'll answer from every possibility. Yes, a regular practice of five or one mantra can be done every day, but it will be much weaker than doing x40.
40 is not a large number actually, it does not take much time.
Try to do your work without interrupting the day. An energy pattern is forming and disrupting it could weaken the spell. We choose 40. But you can also do energy work for just a few days. Keep in mind that its permanence and effect will vary.