However, discoloration and splintering can begin after only a few months. For this reason, most people take on a regular cycle of maintenance. Failure to do so won't cause your deck to rot, but your deck will most certainly become discolored and the surface will become rough and prone to splinters. To ensure that the deck continues to look good with minimal splintering and discoloration, the deck should be sealed as soon as it becomes stabilized within its environment. This usually means waiting a few weeks after the deck is completed before sealing.
Many people never treat and seal their decks.
Untreated decks don't fall down or rot away quickly. Nothing dramatic happens. They will simply get dirty and the surface will become much rougher much sooner. Splinters are a common problem with wood decks. Another hazard is slick surfaces.