That's pretty much been the experience we've had with the ones we've purchased. I think the wife has tried at least 3 different brands/types. You pay more for low voltage lighting but it'll last longer.

I understand the appeal of solar lights; its nice to be able to drop them in the ground without the hassle of wiring. With solar lights, my experience has been that you get what you pay for. I've tried 4 or 5 different brands. All the low cost ones (think under $5 per lamp) tend to have pretty low light the light sensors stop working after a few months. We've had our current ones for just over 2 years and have never had problems with them. They illuminate the path well, last about 8 or 10 hours into the night, their light sensors work flawlessly, and we've never had to replace a battery. Ours landscape lights worked out to about $15 per light on average. Unsure which stores are near you, but we found ours by going to our local big box store's website, sorting by highest rating, and buying the highest rated lights with the most reviews. Pricey? Yes. But we're happy with the look and even happier without the hassle.

So the whole aspect of a solar panel on a light is that it degrades over time and the light becomes less powerful. Just look at the lights u have had for a few years the panels degrade. Low voltage is a better long term solution. Or you just commit to buying new solar lights every few years.