I have not yet replaced mine, but I did inspect them and they seem solid.
Surveyors and insurance companies all have varying views and policies about the issue. US Boat only insisted that the boat be surveyed. I found a surveyor who actually said that he prefers standpipes over through hulls & seacocks because he said if there's going to be a failure, it'll be the valve.
I'm not saying he's right, I'm just telling you what his view was.
Another surveyor told me that he'd recommend on his survey that I rip out all standpipes and replace with through hulls and seacocks.
Bottom line: Call a few surveyors and get their feelings on the issue and what their policy is.