[Edi]

Contrails don't evaporate. They are already vapor. They disperse. Look up the difference between them. The rate of dispersal will vary according to local atmospheric conditions. And the contrails "disappear" only when they have dispersed enough that you can't see the vapor clusters.

Do yourself a favor and go get an education and try to actually learn something about basic science before spouting nonsense about things you are completely ignorant of. There's an old saying about staying silent and letting people wonder if one is ignorant or opening one's mouth and removing any doubts. Applies to this thread perfectly.