Migration Assistant estimated time remaining keeps climbing I'm trying to move my files, applications, and system preferences from a Early 2015 Macbook Pro to a 2019 MBP. Here are the steps I followed:


Got an external hard drive and used it for Time Machine backup of my
old Mac. The total backup was close to 105 GB. 
Booted up the new Mac, created my user account on it with the same name. 
Connected the drive to new Mac, Opened "Migration Assistant" on it, and selected Time Machine
Backup as the option.
On the screen where it asks select the data
you want to transfer, All the checkboxes were selected by default,
so I did not wait for "Estimating File Size", and just clicked on
Next.





I chose to replace the existing user on the New Mac, whilst not keeping any files from it.


 


Hit Continue and let the process start. I first got a few screens such as "Preparing to transfer user accounts", and then said "Looking for applications and documents to transfer (n items processed)"





I left it idle for some time, and when I checked next, it had gone to "Transferring documents" screen, with an ETA of 18 hours 45 minutes. However, with every passing second, the ETA is increasing. It has been an hour since I recorded 18 hours, and it is now at "57 hours 42 minutes remaining" (and counting).




Also, the progress bar has not moved significantly. I can barely make out any movement. 

Is this by any means normal? Should I leave it overnight, knowing that the ETA is not coming down, rather climbing? Or should I cancel it while I can?

I read in a few places that choosing to overwrite existing user account causes this, and advised to create a new user. But there was not enough validation on that post.
macOS progress and completion estimates are often based on the number of bytes transferred.  But one large file will usually transfer much faster than many small files even if they add up to the same size.  What may be happening here is that the transfer started with some large files, went quickly, and resulted in an optimistic estimate.  But now it is into small files which take longer and so the estimate is growing.

The estimate and speed can also be affected by the type of storage, whether the migration assistant is trying to do other tasks at the same time, whether FileVault is enabled, the type of connection for the backup volume, etc.  All of those factors can magnify the differences in file sizes as well as cause variability on their own.

Make sure both the backup volume and the new MacBook are plugged into their respective power supplies and give it some time.  The worst case scenario is a hardware problem with either the backup or the MacBook, but give it a few more hours before jumping to that conclusion.