There are great sealers on the market these days that you can apply annually to help. And the new steam cleaners like Shark that don't use any chemicals also help the sealers last. Alternatively, the porcelain tiles available that look like marble are a great alternative.

The sealers nowadays are great, but we tend to use harsh cleaners in our kitchen areas and then the sealer is removed and your natural stone floor is susceptible to stains, and once marble is stained I'm not sure there is any cleaner that can remove the stain.
I would opt for a polished porcelain with no worries about an ongoing maintenance project.