Actual wheat paste posters can last on a wall for years; our trademarked special paper for wheatpasting is ultra-thin but made from a very high quality card stock which matched with good glue should almost last indefinitely. Wheatpaste campaigns are another story. Typical flight lengths for posters are 2 weeks long however some busy areas in NYC can allow for 3 day campaigns until they are posted over. One of our sales team will be able to give you more guidance on your chosen locations.