Its more annoying than disasterous, to slowly lose pressure that way, in that you have to push it back to 30 every few pours.
I do this with my kegs since I don't have a dual manifold or splitters.
I still use a longer line in those cases anyways though, so I'm not sure on the short line part.
Secondary: GF Czech Lager
Waiting to be kegged, Italian Primitivo
Kegged&Ready: GF Orange&Coriander, GF Honey Lager, GF chocolate ale, GF English ale, Island mist (zinfandel), Island mist (cbry malbec).
Bottled: Infected Mead, Dry Hard ciders, Accidental Sorghumwine, various unnamed.