Ok, so I have a bit of an odd problem. Our site is crawled by google a LOT. There are a few reasons for this, that aren't really easy to change. One of which being you can access localized versions of our site via ita.example.com (italian) and fra.example.com (french) We do 301 redirects if not logged in, and the content wont be localized (think forum posts) but this still causes a large amount of crawling due to google thinking our 50 subdomains are all different sites (not the greatest idea, but before my time and not easily changeable)
I dont want to flat out rate limit google, which I know I can do in the webmaster tools or the robots.txt file
However, 7 year old forum posts don't really change, and dont need to be crawled daily, for 6 of the subdomains.
Now I know I could set an "expires" on the page, but then that would keep it from showing up in google search results, and I could block it with a meta tag, but that would do the same thing.
Is there any way I can specify to google "This is an old page, dont crawl it more than once a year" or something?
If there isnt a way to do that, is there any way to put a rate limit on certain directories?