With so many advantages to switching to a metal Safety Razor, there's bound to be a downside to ditching the plastic. We are so used to throwing our plastic razor around our tub and leaving it sat in water in our shower with no consequence.
But when switching to a metal Safety Razor, you do need to give it a little more love and attention if you want the longest possible lifespan. Give your razor a rinse after every use, you'll want the pressure of tap (shower isn't usually strong enough) against the back of the razor head to dislodge any hair and oil/soap build-up. Then wipe dry, and store in a cool, dry place.
Each time you disassemble the razor to change your blade, use this an opportunity to give it a proper wash. Do not use rubbing alcohol or harsh disinfectants as this can strip the protective anti-rust layer on the razor, soap and water will suffice.
And if you do see any build-up of patina on your razor, a good clean should do the trick. Mix baking soda with a little water to form a paste, rub it onto the razor and leave on for at least 10-15minutes, then buff off. I did this with a razor I let sit in water constantly as an experiment and it worked a charm.
As I like to say, think of your razor more as a piece of jewelry on your countertop!