Take care of your codebase. Keep it clean. A good codebase will enable you to create more great solutions for your demanding customers. If you do not take care of your codebase, then it will rot and your projects (and company) will probably fail.
There is only one way to keep it in a healthy state, follow the boys scout rule: always leave the codebase in a better state than you found it. Whenever you make a change, try to write clean code yourself and clean up surrounding code.
I just gave a lightening talk at Smidig 2008. My talk was about a selection of techniques for improving existing code, how to keep your codebase healthy and why you should do it. Here are the slides and a recording of the talk.