Deck posts are an extremely important part of your deck. So, it should be obvious that ensuring they stay in good condition and a part of any routine deck inspection is critical.
A deck is built for load to be evenly distributed throughout the entire surface area. This suggests the ledger board and posts will have an equal load. This assumption is wrong in most cases. If you plan to entertain on your deck, your guests will have a tendency to hang out at the end of the deck where the railings are; thereby increasing the load on the posts and not the ledger board.