The temporary is valid once issued and signed and is valid for 120 days, yes even when it says pending. You should receive your permanent hard card certificate long before the 120 day expires. Your permanent will not have an expiration date. It is up to the pilot to maintain currency.
To expand on what @Florida Drone Supply said, I received my card in the mail after five weeks of receiving my temporary airman certificate. You will have to take the recurrent test every two years.