old hat

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Behind the times; out of fashion.
• adjective Trite from overuse; overly familiar.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun idiomatic Something with which one is very familiar, or in which one is experienced or skilled.
• noun idiomatic Something widely or long practiced, known, or accepted; something conventional.
• noun idiomatic Something uninteresting, hackneyed, or passé due to overuse or long-standing familiarity.