Last chance for extra mileage runs if you want to keep Plat. (buy higher fares for extra PQMs & RDMs.)
Last chance to fly with 8 others in E+.
Last chance for SDC at no charge.
Last chance for 3 free bags.
Last chance to buy YB fares for instant upgrades.
Last chance to say DYKWIA as a Plat.
OP is going from plat to gold (as am I). Gold still gets free SDC and all elites get YB instant upgrades, so OP will still have those things.