Last year I rode 5 centuries with no problems aside from the usual elation/exhaustion that accompanies such events.
This year we've ridden 4 centuries on our tandem (thinking about 200K and beyond next year, since this is my husband's first year of riding distances & his schedule interferes with training). On our third century, at mile 97, we were doored by a clueless motorist who blamed us for the incident. Front wheel of the tandem was taco'd, our door-hitting-sides were contused and bruised badly. We filed a police report but aside from ice & Ibupr*fen required no medical intervention.
If I worried about getting hurt, I'd never get on the bike.