I recently gave up on a week's worth of downloading my Family Tree on the 21st generation.
It was a shame that the import process basically hung all night every night, because there would be an issue in the data transfer that required a click of a button to re-start the process.
I'm an Internet guy, so I understand API's, data throttling, etc.
But I strongly suggest that it would be a good idea to build in a feature that would automatically click the button to restart the download. Build in a timer that automatically clicks it after x seconds, even have that wait grow longer when throttling occurs.
It just seemed to be a huge shame that the system was unable to work in the wee hours of the morning, when presumably the system load would be lowest, because I didn't stay up all night to click the button.
And, BTW - there seemed to be a major lag the kicked in around the 18th generation. It took 2 days to go from generation 1 to 18, then 5 more to go from 18 to 21, which seems odd, given that we were probably downloading less and less information with each successive generation as lines ended.
Finally, when I gave up and clicked the cancel button, the program hung all day in the cancelling process and had to be cancelled through task manager.