Depends on the design and materials.I tested a macbook pro 16" for a few days and with very little use, the keyboard was already a little dirty with normal finger oils.
I think it's pretty much impossible to keep a keyboard clean.
I have two white Apple desktop keyboards, and I use them daily for two Macs that sit side-by-side on my desk. One is an older wired white A1243, the one with built-in USB ports. While it has a bit of dirt on it right now, it's relatively easy to clean, and the printing on the keys is still intact. The other is a newer white wireless Bluetooth A1843 and it tends to collect the dirt more easily, and the printing on several keys has worn off. Furthermore, the frame is not as robust.
I'm disappointed in the decreased build quality of the newer model. The older model has a firmer feel and I believe deeper travel too.