Rick from Smooth-On... OOMOO or any of our products are guarenteed for one year UNOPEN from date of manufacture (lot number). If opened, we have no way of assuring any future product freshness because we at that point have no control over what the product may or may not be exposed to... typically if you shut the product up as soon as you use it and the conditions are favorable it is not uncommon to get a few months out of an open container... OOMOO will thicken over time in it's container... it is just the nature of the raw materials used to create the product... I know a lot of our compeditors will only give a 6 month guarentee for unopened containers for this reason
Hope that helps