Hilton Honors offers four levels of membership: blue, silver, gold and diamond. A member can have blue membership forever. Higher levels of membership are earned based upon night stays and/or number of points earned.
What is nice about the Hilton program is that as soon as you have enough stays or points you automatically are upgraded to the next level for the remainder of the calendar year. Plus, you maintain that status for the following calendar year.
I find the Hilton Honors membership a great program, allowing me to earn both Hilton points AND airline points with their Double Dipping program. And the bonus amenities as you rise above blue are nice to have.