Theoretically you can sysprep as often as you want to, it's rearming Windows that has a set limit. Each sysprep with generalize switch uses one rearm. If Windows finds it is in state it cannot be rearmed anymore, sysprep fails, logs in C:\Windows\System32\Sysprep\Panther showing an error like this:
In rare occasions I have to re-sysprep I boot to Audit Mode and edit registry changing two DWORD values in HKEY_LOCAL_MACHINE\SYSTEM\Setup\Status\SysprepStatus\GeneralizationState\:
ERROR: SYSPRP RunExternalDlls:Not running DLLs; either the machine is in an invalid state or we couldn’t update the recorded state
- Set CleanupState = 2
- Set GeneralizationState = 7
When done, give this command in elevated Command Prompt to uninstall Microsoft Distributed Transaction Coordinator and wait at least 30 seconds:
The longer you wait, the better; reinstalling MSDTC too soon when it's not completely uninstalled might cause issues. Even on low end slow hardware it does not need more than a minute.
OK, then reinstall MSDTC:
Last but not least delete the Sysprep\Panther folder and reboot back to Audit Mode. You can now re-sysprep without worries.