Need more information on mantras!

Hi, recently I've been using the MILD technique and using the mantra "Next time I dream, I will realize I am dreaming," so far of course it hasn't worked, (I've only used it for about a week.) Before I was using this mantra though, I would use this one for DEILD : "I wake up after every dream period, and remember my dreams." It worked, I woke up at least twice a night (naturally), and remembered my dreams more. Not sure if this is a coincidence or not, but it didn't really help me lucid dream. Now, to get to the point, what are the limits on a mantra? As in, is there a limit to how long a mantra should be til' it becomes less likely to actually work? Because I would like to use a mantra that would help my dream recall, and also induce lucidity inside my dreams. Because while using the mantra with MILD, my dream recall has been poor comparatively speaking to the DEILD mantra. So to say this mantra, "Next time I dream, I realize I am dreaming and remember my dreams," would be too long? I'm not very educated in the whole mantra thing, and I wish I knew more on what it actually did. I only know really that using repetitiveness, it implants a message to your brain to achieve that goal. So my guess is, the longer the mantra, the harder it will actually be to achieve. Thanks to any suggestions, it means a lot!

Here is a good mantra tutorial and here is little more about them Collection ...DILD

1. should be short, but long is fine, if it flows naturally, you don't forget your line, it doesn't make you think too hard about what to say next
2. present tense
3. anything, that sounds and feels right and good to you will work
4. most effective when last thought before falling asleep
5. have the right attitude ("it didn't work, of course" - is not the right attitude)
6. more effective, when you make it rhyme and coordinate it with your breathing. Half of mantra on inhale, half on exhale, for example. Don't let it mess up your normal breathing speed and pattern.

Hope this helps.

My mantra is just "I am dreaming" I use it all day everyday. I suppose mantras are as effective as you want them to be, i.e if you're a strong believer that they will work then they will work well :) Other than that I have nothing more to say, gab has summed it up very well :)