Last year, I believe the lifestyle/airline trackers reset around mid-January, either 1/14 or 1/15. I had loaded $50 Uber Cash on 1/8 as a test, then did the rest of my loading on 1/15 after I saw the meters reset. The $50 from 1/8 was credited back to me on 1/16, and the $100 on 1/15 was credited back on 1/19, so I believe the credits will work even if you spend the money before meters are reset.