The OP's thought regarding age is not idle speculation. The various flu bugs circulating are incredibly virulent and can strike any time of year. I've had bronchitis twice in the last 18 months...once in July and once in March. At 61, I'm aware that how my body recovers from a tough outing is way different than...40 years ago. I live right on the coast and rain is usually accompanied by wind, lots of wind. Now I don't mind a drizzle, mist, sprinkle, brief shower, but I draw the line at wind/storm driven rain. I'll dress/prepare for rain but I've no desire to ride out into a driving rainstorm and arrive home hours later exhausted, cold, sweated out, in the winter or "summer" and get spanked by some damn mutant virus. The other downside is that our maritime climate usually means 50 degrees plus and raining and 90%+ relative humidity. That means profuse sweating while riding and any stoping can mean instant chills. Thus layering.