Archive.org gets their archived pages from Alexa, so to get in the archive, you need to get Alexa to crawl your site.
Alexa doesn't deep crawl sites with minimal traffic. So, you will need to install the Alexa toolbar and visit all the pages you want the crawler to capture... you can check and you will see that the crawler visits within 24 hours.
Alexa donates archived pages to the archive after six months... apparently this is to assuage copyright risk.
Alexa guages popularity via the toolbar. So if somebody with an Alexa toolbar visits a page on the net, it is deemed to be relatively important, and will be crawled -- same day.
Regarding the crawler and your robots.txt, I believe that the wayback machine automatically checks your robots.txt file every time somebody does a search on your site, with minimal caching. This way you could exclude your site's content from the wayback machine by editing your robots.txt file, in real-time.
If the ia_archiver hasn't visited your site in over two months (it takes them two months to complete each crawl), it is probably because none of the Alexa toolbar users visited your site.