Is using Resources.Load too much a bad thing?

Is using Resources.Load too much a bad thing? Is it better to eg make a script 'Graphics Database' where I load all my graphics once, make them static and then just use those loaded graphics by other scripts? Does it even matter?

In my case I've got some planes with Texture2Ds on them - I change them in Update to make some sort of fake 2D animation and I feel I shouldn't put Resources.Load into update.