Lately I've really been moving regularly between large and small works, from 5 feet to 4 inches, which I think has been really good for my creative muscles. Just when I get comfortable working in one size, it's time to switch. It's also great for working out issues I have with a work-in-progress, giving me a new perspective and some breathing room.
Seth Godin recently wrote an article about small being the new big in reference to the challenges that large companies face but I think it can also refer to the challenges artists encounter when facing a large blank canvas. Sometimes it can be difficult to get those interesting, fluid, noticable marks on a large canvas...you know those marks that can happen accidentally during the process. Also, I think we're often less intimadated by a smaller surface...maybe because it doesn't cost as much so it is more forgiving. Working small also doesn't require as much in the way of materials or time.
Anyway, I love working big...like really, really love it...but I have to admit that there is an intimate, happy feeling to working smaller. It's a good mix.