jecasc - 5:13 pm on Jan 7, 2012 (gmt 0)
Well... if domain information had an impact on Search ranking algorithm, I would bet that your "private whois" would take any positive impact a long expiration date might have away. Tenfold.
Personally I do not think it has any impact on rankings.
If I had to improve a website for search engines the domain expiration date would probably number 13,945 on my to do list.