Learn Spanish (Latin America): Hacía diez años que la tienda permanecía cerrada. - The store had remained closed for ten years.

This sentence describes a situation that was ongoing at a certain point in the past. Using hace... que with the present tense (like permanece) would mean the store has been closed for ten years and is still closed today. By using hacía... que with the imperfect tense (permanecía), it means the store had been closed for ten years up until that past moment in time.

Could I just say estaba cerrada instead of permanecía cerrada?

Yes, you absolutely could! Estaba cerrada means "was closed," which works perfectly here. Permanecer means "to remain" or "to stay," so permanecía cerrada is just a slightly more descriptive way to emphasize that it "had remained closed" for all that time.

Why does cerrada end in an "-a"?

Here, cerrada (closed) is a past participle acting as an adjective to describe the state of the store. Since la tienda is a feminine singular noun, the adjective needs to match its gender and number.

Can I change the word order to put the amount of time at the end?

Yes! You can flip the structure and drop the word que. It would look like this: La tienda permanecía cerrada hacía diez años. Both ways are completely natural and mean the exact same thing.