Maca, horny goat weed, lecithin, l-arginine, lysine, and zinc have all been bantered about , and you will find in other message boards some mixed results across them. My guess is different supplements vary from person to person, along with the standard help from:
1. abstinence 2. foreplay (but not too long) 3. edging 4. position of cock 5. technique and 6. degree of being turned on (I believe in the last making a difference at times).
For some... they lay claim of instant results, others point to a 3 week regimen... course that's "internet speak", so who knows.
With the "technique" part: experiment with grips n' strokes... I now know how to shoot like sprinkler head, shoot far, dribble/pour out, and how to shoot many many ropes [same total volume, just thinner and more ropes].