5 months (above). A year, below:
Last April, I did post with a photo of a neighbor's juniper bushes, showing the remains of some toilet paper somebody wrapped the house and yard with on Hallowe'en 2010. After five months and some fierce rains, there were still bits of it hanging.
Here's the same view today, a year and a day, after the draping.
Forget the presidents on the Dakota hills; toilet paper (and Twinkies), them's the way to go for an enduring monument ...