For some of the early Polaris submarines, the Polaris A-3 was the end of their upgrades, but a large number of them (about 31) were further rearmed with the more-advanced and longer-ranged two-stage Poseidon C-3 missile.
Some of the initial Polaris submarines reached their peak upgrades with the Polaris A-3, but a significant portion (about 31) received an upgrade to the more sophisticated and long-ranged Poseidon C-3 missile.