We have been using plastic carboys for many years. Never had a problem, except the ridges or shoulders that are built into them to retain rigidity. These ridges cause a lees/sediment hangup. For final clarifying we go to glass because the carboys are smoother inside. Now it's hard to find glass that doesn't have ridges on the outside to inhibit your view of the contents. We have stored/aged wine in plastic for two or three years with no problem. We bottle in PET bottles almost exclusivly.