If you have that many photos I would suggest you upgrade to Aperture as that is designed to manage large photo libraries.
Thanks, it appears that Aperture is the way to go once needs grow beyond iPhoto. I believe, it is possible to start with iPhoto and than migrate to Aperture later. I can start with importing only recent last couple of years of pictures in iPhoto and than, as library grows, move to Aperture. Do you see any issues with that strategy?