I ride mellow 30 mile rides in jeans all the time. But, bike shorts too cold under 65???? I'm generally not going to wear (long) jeans unless it's under 55.
I have some work pants I'll ride until it's 65 or so. They're kinda like the Dickies of yore, before they got super baggy. They're way better than Levi's 501s for riding.
Some people are really scared of jeans, but after riding to work and back in them everyday (30-40 mins total) for several years, your skin toughens up a bit, and even 50 mellow-paced miles in jeans is no problemo.