Remember the old AT&T commercial "Reach Out and Touch Someone?" (OK, if you don't remember this just work with the concept).
It is difficult to assess, some people feel comfortable with a distance where they can't be touched without their opponent having to take a step or move in their direction (thus you would be aware of their intentions), while others like to be "up close and personal" in order to stop the attack from happening (i.e., pre emptiveness, being pro active, staying ahead of the curve, or just not getting hit).
As far as Maai goes, my good "Abuela" put it this way: "keep your enemies close, so you can watch their intentions but not close enough for them to touch you." I could not believe it, but her wise words came back to me the other day at the dojo- perhaps a vision of my good Grandma.
By the way, she never did Aikido but she could smack me with the house slipper from 8 yards out!! And she never missed. . .