I have an old pair of plastic boots (Scarpa Omegas) which I bought new around 2007. I haven't used them much in the past few years (most of my recent winter outings have been day trips in single boots) but was thinking about some multi-day mountaineering trips this winter season. The Scarpas are still in decent shape though a bit scuffed up. I recently walked in them for a few miles and they are still relatively comfortable.
My question is this - Scarpa's literature recommends not using plastic shells that are older than something like 5 years. I assume the concern is that the plastic may lose plasticizer over time and become brittle. The boots seem to still have some life in them and I know some people use plastics for many years, though Omegas are thinner than Invernos (for example) and I assume might be more likely to fail over time than heavier plastics. Is there a reasonable way to tell whether the boots are still good other than to just climb in them and see what happens?