One minute? Um, no - not with normal projectors anyway. I've projected them for a lot longer than that, but it IS true they suffer from light fading while being very resistant to dark fading, which is one reason they used to make a lot of Ektachrome dupes for projection.
Originally Posted by Tom1956
I don't hesitate to project mine occasionally, but I'm mindful not to leave the same slide up too long. I've certainly exceeded a minute though with no harm, repeatedly.
It's worth it, absolutely, to see them as they should be seen.