There is really only two different ISP's you can get where I live. One of them is Verizon, which I don't have, so I can't know what their TTL is, but my ISP I know (with a 95% certainty) that the default TTL is only 10 minutes. But still, I understand what you're saying.
It doesn't seem as if I have many choices unless I can find a free DNS host.
(Or I could install portable XAMPP on my flashdrive. Knowing me, I'd forget to save backups of the site, though...)
http://afraid.org