This is a little off the center of SEM, yet I felt many out there have
some experience with my current situation and thus may have some
benchmarks to offer.

Situation. My e-merchandising client is in process of an entire re-
make of the website. An unavoidable consequence is all the page URLs -
save the home page - will change. The site is mature (10 years old)
and a number of pages have earned their way into strong positions in
organic search rankings and their sales are very heavily dependent
upon this positioning. We are retaining tag and copy text that are
relevant to SEO and plan to do a number of 301 redirects to give the
new pages a leg up.

I am aware that it takes a period of time before old-no-longer-active
page URLs disappear from the search engine indexes. I am also aware it
takes a period of time before the new page URLs appear in the indexes
and appear in their "natural" ranking position.

The info or experience I seek from you are: 1) How many months might
we expect our no-longer-active Page URLs to remain in their search
engine ranking position before they get removed? 2) How many months
might we expect it to take for our new Page URLs to attain their
natural level in search engine results?

Greatly appreciate any insights.

Thanks,

Roscoe