If you feel that they are over-crawling your site (perhaps even missing deeper content) you should ensure that your HTTP headers are returning good values for things like 'lastmodified' time etc. It may be that Googlebot overestimates how much your site is changing. As a bonus your site will behave better with regards to caching (be it proxy or browser based) and thus feel a little faster.
You'd do well to study what URLs are being crawled (by reviewing your server logs). If they are recrawling the same URL again and again, you definitely have a problem. A common variant on this is if you have a page that can be displayed in many different ways using request variables. Googlbot may try to crawl every possible combination of those variables.
An example I've encountered as a crawl operator was a page that had a list of twenty headings, any combination of which could be expanded. Basically, that page had 2^20 different URLs!
Make sure that Googlebot isn't stuck crawling basically the same page over and over again with trivially different parameters (I've seen it get caught up in this)