Imagine you coming back to the game after 2 years to check your investment and all your airdropped SPS is gone. This is essentially "stealing" assets from inactive players, which IMO is a really bad and shady practice.
No, it's not "yours", there is no reason to keep the airdrop forever.
RE: SPS Governance Proposal - End SPS Airdrop Claims & Send Unclaimed SPS to DAO