I've done a few searches and can find nothing posted already, and can't see a more appropriate section....
I have a 3-piece suite that is well over 10 years old but I have worked away from home for a lot of that time and live alone, so it has had very little use at all. But, the seat support of all pieces has collapsed.
I have bought some new 8 gauge zig-zag springs and fitted 5 to one arm-chair, above the old springs. They have made some difference, but not much.
Is a DIY re upholstery job worth the effort? How much is the age of the foam seats likely to be a source of the problem?