It is interesting to watch composers work under pressure and time constraints. When there are deadlines to be met, you have to go with what you know will work. There is something about the sheer craftsmanship of assembling sounds that allows you to assess a composer's ability. Educationally speaking, that is appropriate to do on occasion. For example, during my comprehensive examinations, I was placed in a small room and given a theme which was a tone row, and I was told to write a theme and variations for flute and piano that contained an opening presentation and at least two variations. It was a three hour question, and I thought it was a superb way to assess me.
Naturally, when you are under pressure to finish a composition in three hours, you go with things that will work. In many ways, I imagine that this is how many film composers work. They assemble clichés that sound like Mahler - or someone similar, and they try to work in little bits of creative freedom into the constraints of the very limited harmonic vocabulary that the movie going public will accept. I have tremendous respect for the speed and ability at which those composers work.
What concerns me is when a composer completely devolves into an assembler of musical clichés. I think we all have to do it sometimes. I sometimes write a commission for someone that wants a piece in a certain style or harmonic vocabulary. I enjoy the challenge of that. I try to work in bits of creative freedom into the constraints of the harmonic vocabulary - even when the cliché may be my own "style".
The way I try to keep balance is to always have something simmering on the stove in a more adventurous vein. I always try to work on something that is pushing boundaries or rethinking problems. I have to believe that the commitment to exploration will hopefully affect the work that occurs under time constraints. I hope that the exploration allows the assembly work to become more than a simple linking together of musical ideas that "work".
Sadly, I often wind up seeing composers simply cranking out things that work. They "cease from exploration" and are often rewarded greatly for doing so. This issue, by the way, has nothing to do with "style." It happens to composers who write tonal and atonal music. It happens to composers of popular music and serious music. It's especially prevalent in contemporary musical theatre.
So, keep something good simmering on the back burner. It will keep you healthy and sane.