As long as you have your RAF, level a whole bunch of classes.
You never know what you'll find interesting a year from now.
Or what might be buffed/nerfed to the point where you want to try something else.

Also, even if you're not actively playing a toon, you might still get something out of having a toon high enough for a given tradeskill.
Even if you're "milling" for your inscription toon, doing it with five toons only takes 20% as long as with a single toon.
Plus, you might benefit from an "army" of alchemists/tailors/etc for the once every 24 hours transmute.

More options is better than fewer options.
RAF is a building block for later fun.