I have Ortlieb Back Roller Classic panniers. They came with a shoulder strap, but I don't use it because my walking distance with the bags is short (from bike rack outside the office to my desk). The shoulder straps are somewhat thin looking. I was always thinking that if I had to carry them any distance at all, I could try the Ortlieb straps, and if I didn't like them, I could detach the shoulder strap from my leather computer case and just use that instead of the Ortlieb strap.

I don't know if that helps at all, since I haven't done the walking you are looking at. I can definitely confirm the quality and durabililty of the Ortlieb bags in general, though. I will keep mine forever, I just love 'em.