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.