When you switch-on the time stamping in the Serial monitor, you get printouts like this:
13:45:23.848 -> getData: 13:45:24.553 -> getData:
This looks like the 2nd getData command came ~700ms after the first, while in reality it came several minutes later!
The problem is that the time stamp seems to get printed out with a \n character. This thus becomes a meaningless value when the next print comes much later.
Instead, the timestamp should only be printed at the time-point a new print has begun!