Microsoft file migration tool + Robocopy subsequently

I'm migrating from Windows server 2003r2 to Windows server 2012r2

Have most steps under control but looking at the file migration and share creation.  We will add DFS on the 2012 server, none now.

Was planning to use the Microsoft file migration tool, would like to do it several days prior to catch any issues before the cutover date. if I complete both phases of it (including Delta copy), would there be any issue if I then used

ROBOCOPY "\\server1\dfsroot" "\\server2012\dfsroot" /MIR /DCOPY:T /SEC /R:1 /W:1 /NP  /LOG:d:\robocopy.log

Each night to keep the new server in sync and then once just prior to cut over? I assume OK since the shares would be created and this would copy NTFS permissions on any new files.

Also, is there 100 GB limit on the Microsoft migration tool? I heard that somewhere...

https://blogs.technet.microsoft.com/canitpro/2014/11/05/step-by-step-migrating-a-2003-file-server-with-microsoft-file-server-migration-toolkit/

Thanks much!