301 ? - Time Frame & Effect

Looked around, but can't seem to find an answer to this ?

I changed the name of my page one year ago. 301 is still active.

On a SERP result, my old page URL still is displayed...on click, it 301's to new page that I requested as normal.

1) Why didn't the page get renamed in the index after so long.
2) Why is there still a cache of a one year old page that was redirected?
3) Could this cause duplicate issues if two pages are cached with the same content even though 301 to current page.

Canonical tags are used in all cases.

Redirected about 10 pages 12 months ago, 2 are still indexed and cached, very strange....

Double check to make sure it returns a 301 status, not a 302, 200, or anything else by entering the old URL here:
http://www.seochat.com/seo-tools/redirect-check/

Thank you---was getting 302....changed to 301...

Thanks for answering, much appreciated