Depends on how they are tied to the pc and the update rate required. If they are connected using one interface port I would use one loop. If questioning them in 1 loop doesn't satisfy the required value update speed I would split them up in multiple loops. Maybe it is necessary to even use multiple interface ports or IO cards.
When you are seriously thinking about using 30 loops, have a look at dynamically calling VI's in combination with VI templates. In that case you create one Vi for the acquisition and just start it 30 times with different parameters.
Regards,
André (CLA, CLED)