Pretty much unless I need to work to a certain size or format.
I do a lot of murals and I'm working on a 1m square canvas right now.
In that case I either work to the finished size (if it fits in the work area) or a scaled down version.
Vectors can be re-sized to any size and not lose quality but the only exception is where you use raster (photoshop filters/effects).
You need to set the dpi of these in preferences and make sure they scale when enlarged.
This also applies to things like stroke widths and things.
Out of the box these things don't scale up proportionately and you have to set it to do so.
Even though Ai works in vectors which is mathematical I've found it does have its limitations and is not always that accurate.
Working too small is defiantly not advised as odd things can start to happen.
I usually try to stay at the same scale when I'm working on something so that when I nudge lines and nodes around the steps stay uniform
Same applies to the settings of a lot of effects and actions.
I've also found that sometimes it doesn't always perform a task as accurately as it should and sometimes they're a little off.
Technically speaking that shouldn't be but it sometimes does.