As reported in the Loyalty Lobby blog, Hilton now allows you to “Restore Your Points” after they expire. The cost is 1/4 of a cent per point for up to 100,000 points. That will cost $250. Any additional points, up to 1 million, can be restored at no added charge.
You can restore points up to 18 months after they expire, but the Terms & Conditions state that you can do a restoration only once.
Hilton brands include Hilton Hotels & Resorts, Waldorf Astoria, Conrad, Canopy, Curio, DoubleTree, Tapestry Collection, Embassy Suites, Hilton Garden Inn, Hampton, Tru, Homewood Suites, and Home2 Suites.