having the page where my link is located being cached is very important to me as well. i also make sure that the page isn't a link farm. more than 100 links per page.
I check to see if my link is among competitors. I don't mind the link being among those that compliment my service or product, but to have competitors listed defeats the purpose of the link exchange, IMHO.
I look at the page rank of the page in question. I see no benefit giving available space to link exchange partners which give no credit back for page rank.
page rank is over rated. i make sure the the page is cachable and when the last time it was cached. i also make sure that the page doesn't have over 100 links on it; better if only 50 or less.
One good embedded link--that is one surrounded by content it is integrated into--is worth 1000 links-for-the-sake-of-it. I look for pages that genuinely endorse a link to a readership.
I make sure no more then 10 links are on the page, on high pr sites, 15 max. Also I make sure theres a fair amount of backlinks to there website and I check to see if the age is 6months+ sometimes as well.