Hi 11bee,
I've found a recent advantage to using a clear sealing over my decals:
I airbrush Tamiya X-22 acrylic clear coat before applying decals, after decals are applied I just airbrush X-22 over them. I then apply Tamiya panelines which is a thined down enamel paint over panel lines. Because of the process I've used I can also paint panel lines over the decals which creates a really cool effect. When I rub off excess paneline paint off with an enamel thiner neither the paint or the decals are attacked as the enamel thiner doesn't work on acrylic.