wrote...

One thing that I have gathered from all these discussions is to use a
board (or solid foundation ) rather than a box spring for better
performance of most mattresses - and as someone suggested get cheaper
versions and change them often

Though bad foundations will cause problems, there is no need to discard a good
foundation. A piece of 1/4 or 3/8" plywood between the mattress and foundation
also works as good as a solid platform.