Via OMaaT, the Chase Hyatt Card’s signup bonus will be changing from two free nights anywhere to 40,000 World of Hyatt points on June 29, 2017.
40,000 WoH points is equivalent to two nights in a Category 5 property.
Points won’t expire as long as you have activity in your account. The two free night certificates from the current signup bonus need to be used within a year.
Two free nights are more valuable if you are redeeming for a Category 6 or 7 property.