"But the question is will there be other consequences of exporting and then re-importing?"
Exchanging GEDCOMs with other software programs has pitfalls of its own, as you've noticed already with the Quarter days that FTM doesn't support. If this data is detailed at all, I would be surprised if this is the only problem you have with it.
GEDCOMs generally contain less information than the software programs that produce them. That's because the GEDCOM standard is like a least common denominator for data exchange. So, when you export to GEDCOM, you will lose all of the data that can't go into a GEDCOM. This isn't a big worry for FTM users though, since FTM generally offers functionality that falls short of the GEDCOM standard where other programs offer features that exceed it. Nevertheless, it's something to be aware of, and the only way to see if all the data made it is to compare what you started with against what you exported.
Anyway, I can't answer your question without knowing what you did with the GEDCOM in FTM. Did you import it as a new tree? If so, what you did (export-modify-import) should have no effect. If, however, you imported the data into a larger tree, then you might indeed have lost or changed some data along the way.