Windows that won't stay up: prop rods don't count

A window that will not stay open on its own — sliding down, needing a stick or a book — is a deficiency, and the prop does not cure it. Balances, springs, and sash hardware are turn items most crews rush past. What is your test during a pre-walk, and which window brands in your stock are the worst offenders?

The prop stick is the tell that a window has been failing for a long time and everybody made peace with it. Balances are not glamorous parts, but they are cheap compared to a cite, and a pre-walk where somebody actually raises every sash takes minutes per unit. The windows that slide down also tend to be the ones that do not lock right, so one fix often closes two problems. Which fix has lasted longest for you on tired double-hungs — new balances, spring kits, or full sash replacement?