Same thing happened to us, we ended up replacing the coil. Ours was under warranty (10 year) so the part was free just paid for labor and refrigerant. Might want to call the manufacturer yourself to inquire.
As said, it should last longer (your outside unit) so I probably would not replace if you have no other issues. The only caveat to that is, if you do have an older refrigerant like r22 you will want to replace the unit because it's getting more and more scarce and as a result ridiculously more expensive. I would definitely verify what is in it yourself. Should have a sticker on the outside unit if that new.
[Post edited by Tombo at 06/16/2017 7:45PM]