I've hit that point. That point when you're building your game ideas, mechanics etc when you suddenly think "but what if I ripped all of this out and did this i...
480px (30 times character width) does seem a little too big.
Maybe do some tests with 320x180 (20 times character width) and ask for opinions of people around you.
It depends on the style I end up going with - which to be honest is still a loong way off!
Sometimes that size with 16x16 tiles can work, (like in that gorgeous work by Raymond Schlitter) depending on how the rest of the tileset comes together. But I'll bear it in mind, I do have a list of 16:9 ratios that I could use!