Just to calm your fears a bit. Many times I have got to the end of the project and found it has to go on a diet.
I have two major techniques to deal with this, one of which is relevant.
In the build system I add a quality setting for audio, and I lower the quality of sounds I think don't need to be full quality. I don't change the source files, I change them in the build system. Which means I don't have to tell any of the sound guys what is going on.
I have done this many times, and never, ever, has anyone noticed.
You should have no problems putting them on a diet.