Hilton Honors has extended the expiration period to two years:
https://www.hilton.com/en/hilton-honors/terms/
says:
"
Members who do not have eligible activity as defined in a. - d. below in any 24 consecutive month period may be removed from the Program and are subject to forfeiture of all accumulated Points. At the discretion of Hilton Honors, such Members may be permitted to remain in the Program and removed after five years of inactivity. To keep accumulated Hilton Honors Points, the Member must take one of the following actions within a 24 consecutive month period: (a) stay at a hotel within the Hilton Portfolio pursuant to the terms herein; (b) earn Hilton Honors Points through any third party source of Hilton Honors Point accumulation, including a Hilton co-branded credit card, pursuant to its terms; (c) purchase Hilton Honors Points; or, (d) donate Points through The Hilton Honors Giving Back Program."