UV problems outside 0-1 space?

The question is, has anyone run into issues with models or levels by having any UVs outside the 0-1 space?

Several objects have different Mat_IDs, however those Mat_IDs are out of the 0-1 space, mainly for ease of use outside Unreal.
Never ran into problems before, wondering if anyone else has had any issues with that.

Image examples show a computer monitor, broken out for monitor’s screen, buttons, and labeling.

I’ve never encounter problems with this method, but I’ve been told there are “issues”.

Anyone out there knowledgeable in this?