I just use the white plastic labels and use an HB pencil on them.
That stays on clearly for the whole growing season in the greenhouse, indoors and outside growing conditions.
I bought the last batch from the pound shop four years ago and I have cleaned them each season.
Cleaned them all again last month for next year. Just a quick light scourer scrub in cold water does it for me.
Only about a dozen or so of the hundred or so I bought then have gone brittle. So not as I have added much plastic to the world.
Been doing that for many years too and in the past found it was about three years that most became brittle, but this last batch seems to be holding out a lot better.