Another 'Keep the Original' fan here.
You might just need it later.
Conversions do not always go as smooth as one wishes
Conversion of a conversion is usually a worse idea. (IMHO Edit the converted book to put the fine finish on it. Not convert it again)
to 3 state status columns (preferences: Behavior: Yes No columns ...
Yes means looked and it is good to go
No means you looked and it failed (the first go)
blank means you have not looked