Question about legnth of time misdemeanor shows on record?

What is the name of your state (only U.S. law)? PA.

It NEVER goes away entirely. It's not like a credit report; items don't automatically drop off after x amount of time. Once it's there, it's there forever.

IF you are able to get it expunged (which depends on state law as well as what the misdemeanor is) that limits who can see it, but it never goes away altogether. It's there to stay.