Hi. No, this process does not take so much time. There is a problem in your stack, probably. Make a double check in it:
1. Check the file system of the units in the stack. All of the switches need to have exactly the same firmware version, and the same.
2. Check the sysname of the units; all the switches need to have the same sysname.
3. Check the physical connections of the stack cables.
If all the requirements above are ok, I would suggest you to perform a firmware upgrade in the whole stack, then reboot it. Sometimes even a .cfg file with a different name or that is corrupted can force a sync loop.
HTH