I totally agree with you that they are very convenient and lot cheaper than running power to a motion light, unfortunately for me, mine haven't blasted two years so I guess I've bought the bad ones.I bought a pair for my neighbor for her sheep barn and pasture. Before that, she was wearing a headlamp to feed the animals before going to work. I didn't expect much. To my amazement, they stayed lit all night (dusk to dawn - dim), and lit well when they detected motion - even in sub zero weather. This is their second year and they are still going strong. She loves them.
My main point was that Solar LED lighting takes a huge amount of cost out of lighting a trail.