In reply to James Oswald: It probably wont be, thats why its supported...
"The Stanage Bus is supported by Sheffield Passenger Transport Executive, the Stanage Forum, the Peak District National Park and the Access and Conservation Trust (ACT)."
Yep - 5pm is way too early for me. In the summer I'd be more likely to still be climbing at 7 or 8pm, so I'd miss the last bus back by 3 hours or more. But I suppose for earlier risers than me it could work out OK.
You could always bet the bus out then hitch back. Its always been very easy to hitch back to Sheffield from Stanage or Burbage, less so in the other direction.