I've done hundreds of centuries too, the first back in 1978. Most have been with at least one other person, but I've ridden several alone too. In fact, I used to pre-ride proposed century routes for my bike club when I lived in MO.

There is a very tranquil self-sufficiency about a lone century, and while they are fun, I kind of like riding with people too.

Odd story: Once I was riding a lone century and I was almost out of water, with no clue when or where I might be able to find more. A motorist in a VW Golf pulled up next to me and shouted, "Do you need water?" No idea where he came from . . .

So I said, "Yes, I'm almost out!"
He said. "Give me your bottles"
Very stupidly, I did.
He took both my bottles and drove off.
"Am I stupid or what?" I thought to myself.
I rode along wondering just how I could be that absolutely stupid to give my only two bottles to an absolute stranger. Sheesh, . . .
Then, a mile later, I saw this same gentleman, standing by his VW Golf, holding my bottles aloft.
"Here you go!" he shouted.
I grabbed the bottles, now heavy with ice water.
"Thanks!" I shouted, not feeling quite so stupid after all.
To this day, I have no idea who he was.

Rick / OCRR