Originally Posted by HarryT
Voluntarily, or are those the Hugo rules?
Voluntarily. There is no Hugo rule about how many times you can win.
Previously, artist Michael Whelan removed himself from competition for similar reasons after winning a dozen Best Artist Hugos (often back to back).
The official rules governing the Hugos are in the WSFS constitution, here: http://www.wsfs.org/bm/const-2009.htm
(Scroll down to Article 3.)
A useful FAQ is here: http://www.thehugoawards.org/hugo-faq/