Riding brevets, particularly long ones at 400 km and up, OOS stints provide essential relief. Really it's a relief of everything that's been in a steady state for a long time - butt, hands, neck, low back, shoulders. If I'm on a long stretch without a hill to climb, I'll ride OOS for a bit just for a break. If we're pacelineing, my turn on the back will include OOS time to break things up. In that regard, occasional hills that provide a reason for 30 seconds OOS are welcome.