When to stop optimizing and focus on site redesign

[JagggsWaggert]

I have decided to completely overhaul a corporate website and convert the site into a CMS. In preparation for this redesign I have consulted with an SEO company and they have given me a list of recommendations regarding coding and content.

The website redesign is 3 months away. Does it make sense to optimize the old outdated site first, or focus on applying my findings to the new site? Management is eager to get started so that they can validate the researching phase.

Are there any associated risks with investing in the link building aspect of this project with old URL structures, only to have those links change (resulting in massive 301 redirects)?

[tstolber]

Links will be of value regardless of the site design and as long as 301 redirects are put in place when the new site goes live that will be OK.

I see no harm in starting to link build now.

[realityhack]

Go ahead and link build. Make sure you redirect all the URLs. I wouldn't bother with on-site optimization. You won't get enough data in that time.
Depending upon your goals you could A/B split some of the new text etc. but that might not tell you much out of context.

I would focus on making the new site top notch. Then refine from there.