I've had the same 2 buckets for 10 years, which were my primaries when I first started, now are my cleaning buckets. With the correct mixture of pbw to water OR starsan to water, you shouldn't have any issues. Although I don't typically soak anything overnight as it's not needed. Just a couple hours at the most and stuff should be clean or need a gentle brushing with a sponge or bottle brush.
I could see how chemies would damage the food grade plastic buckets for homebrew if they were used improperly. Or if you used chemicals that weren't supposed to be mixed in plastic. There's also the storage of the plastic and it's ability to withstand certain temperatures (ie. left outside in the heat of the summer or through cold winters). Maybe certain types of plastic can be eaten away by PBW. I know teflon can get completely screwed by PBW if you use it.