I personally think in developing a personal language, composers need to strike a balance between indiscriminate absorption of everything they find, and limiting themselves to an overly narrow range of influences. I know the process varies from composer to composer, but I think it's important to find that balance. It's different today, where we have more control into what feeds our composer's mind--we kind of need to carve a personal ecosystem out of today's chaotic musical world. I've found it helpful to have a diverse cluster of a few core influences as a reference point (Sibelius, Messiaen, Britten), and then kind of expanding outside that. Polystylism is a fascinating approach, though it's not one that works well for my own process. If I composed in whatever style interested me at the moment, I don't think I would find the motivation to complete any full pieces. Again, it really depends on the composer, but as for me, my music is usually an expression of a philosophical vision, or a way of life. I can't really separate the styles and systems from the musical vision that bred them.