It all gets brittle eventually. Try digging up your sewer pipe, give it a tap with a shovel and see how easy it cracks. That's why the "Sewer Lawyer" can afford all those commercials he's running now.So the pvc conduit won't?
But if you go with conduit it'll hold up for the rest of your lifetime barring land shift from earthquakes or land slides. Remember to run a bend at both ends and/or seal it up to keep water, bugs, or mice out. 2" is great for mice to eat your wires as they're building nests.
Also any Sch 40 above ground will get brittle over a summer or two in Oklahoma.