The plastic sticks certainly last longer than wood Popsicle sticks. I've found that on the smooth plastic tag surface of my bed labels, Sharpie permanent marker will often rub off completely with a dry paper towel. Since I use so many sticks for my seedlings, I go with the wood Popsicle sticks for those (available in a box of 1000 for cheap, at Walmart, or box of 500 for the "tongue depressor" size--in the crafts section). The wood sticks have usually rotted at the ground level, by the end of the summer, so they might be thought of as a soil supplement.
Bob
EDIT: In the past, while tilling the spring garden, I've unearthed completely intact plastic nursery tags from vegetable varieties that I hadn't planted for many years.
Bob
EDIT: In the past, while tilling the spring garden, I've unearthed completely intact plastic nursery tags from vegetable varieties that I hadn't planted for many years.