Valid January 6 2020 to May 3 2020. Must register on their website. Hilton had a similar deal in early 2019 as well.
Registered Hilton Honors members will earn 2,000 Bonus Points per stay during the Promotion Period. Registered members will also receive an additional 10,000 Bonus Points for every 10 nights completed. The 10,000 Bonus Point award can be earned an unlimited number of times during the Promotion Period with this offer.
What is the Promotion Period for the "Points Unlimited" Hilton Honors promotion?
January 6, 2020 through May 3, 2020 ('Promotion Period')
How will the 10,000 Bonus Points be awarded?
If you stay 10 nights within the promotion period, you'll earn 10,000 bonus points.
The 10,000 Bonus Point award can be earned an unlimited number of times. Each time you reach 10 nights, the count resets. If you reach 10 nights in a stay and have additional nights during the same stay, the additional nights will start counting toward the next 10,000 Bonus Point award.