How long do college credits last?

It depends on the college, and sometimes on the subject matter of the class. Most colleges only will let old credits "count" for five years after you took the class. Any longer ago than that, and the subject will have changed too much for that old knowledge to be relevant. But that does vary by the college.

You'll need to ask the school you're about to go to about those old classes. It's possible that some, or even all, of them may still count, but it's just as likely you may need to retake some of those classes. Be prepared for anything!

Know that most colleges do allow you to take CLEP tests to prove that you have the equivalent knowledge to a college class. So if you know you know that Freshman English stuff, if your old Freshman English class is too old to count, you can ask about testing out of the class.

It's up to the school you want to attend whether they'll accept credits that are that old. As to retaking those classes, consider whether you'll need them for any future classes you'll want to take, and how confident you are that you still "know" the material.

It depends on The college and the university guidelines.

You need to go talk to the student adviser. Doesn't matter what anyone says on YA.

Depends on the class and your grade. Most of the time if you received a C or lower, you have to do it over.

If the credit was in something technical, say a pharmacology you would most likely have to do it over (new info) most other things are good ....forever.

I was told 7 years

as far as I know, forever, just like a bachelors degree, associates degree, or masters degree. No expiration date.