Last for about 50-60 builds, then needs to be replaced. I am using a paint scrapper to get the parts off of it.
Sometimes when the PLA won't stick to the sheet, I use my heat gun to warm up the bed. Make sure you do not burn the sheets (because they will burn), just heat up the bed. Then the print has no problem sticking to the dremel build sheets. To remove the build, again, I use a paint scrapper that I sharpened the edge with a grinder to a knife like edge. This allows the edge of the paint scrapper to get under the build and I can pop it off.
The hardest part when replacing the build sheets is when you have to re-level the print head using the paper provided. If you do not get it perfect, the builds will be pressed hard on one side while not adhering to themselves on the other. So make sure you get your build table perfectly level.