You are correct. None of these are sustainable and their effort to result ratio is way too high. In fact most of these DILD techniques are based on false assumptions and have no real value. It's a pity that people won't admit it and keep misleading the beginners with this.

If you want something more sustainable I think you should practice the more on demand methods. Not the typical WILD techniques though. They are also misguided and won't give you good results. IMO, a combination of SSILD and DEILD will give you the most consistent result and once mastered, will take minimal effort to execute. In addition to being a very effective technique on its own, SSILD is very effective in conditioning your mind/body for a "phase" to happen. I'm using Michael Radguda's term here because I'd like to recommend his variation of DEILD which he calls the Indirect Techniques. These techniques will allow you to catch the many awakenings during your sleep and turn them into lucid dreams. When you combine them with SSILD, which causes not only more awakenings, but also more stable trances during these awakenings, you will have a much higher chance to become lucid. This combination, if mastered, can literally give you 100% success rate with minimal effort.