if you attatch a shady spectacles to a clone mirror unit. and you make it copy another card again, does it lose temporary?

No — the Reflection keeps its granted Temporary and still dies at the start of the next Beginning Phase.

Copy effects only replace copyable traits (Name, Type, Tags, Cost, Domain, Rules Text — Rule 477.1.b.1.a). The Temporary Mirror Image granted isn't a copyable trait, so Shady Spectacles' "becomes a copy" effect can't see or overwrite it. Since that grant has no stated duration, it lasts as long as the token remains on the board (Rule 801.3.a.3), so it applies on top of the new copy.

One nuance: if the token had copied a unit whose printed text includes Temporary (e.g. a Sprite), that copied instance is replaced by the new copy — but the Mirror Image grant still remains, so the token stays Temporary either way.