You don't want to break that seal unless you have to fully inspect it or replace it. If your worried about air leakage, put a cover over the unit and removed the inside cowl and fab up a piece of insulation for the opening. As soon as a water leak starts...the damage is done (I know).
edit... referring to a roof mounted unit, not side.
*Currently trailer-less but shopping
07' GMC Envoy w/ P2 controller (current TV)
88' Chevy K5 Blazer (soon-to-be TV)
74' VW Superbeetle (1303)