I think I let my first flower go too long before attempting to extract pollen as well. I gather that the anthers need to turn yellow, but not as far as orange, when extracting pollen. Can it be done repeatedly if you don't remove the anthers from the flower?
Yes, that is true.The petals on my H. minor flowers didn't fall off. They turned green with a bit of a pink flush.
What I was told is that the tip of the stigma turns black when pollination is successful. It can be quite difficult to see though.
Heliamphora don't have petals, just tepals, and they never fall off. The "bulb" is always there, but if it starts swelling after the anthers fall away then you know for certain it's pollinated.