Please accept this reply as my application to join the "SBC Club"

"Are you, or is anyone else you know, primarily a solitary bicycle commuter of many years?"
Well, perhaps not "many", but I'm getting there. Started back riding in '02 at age 50, after not being on a bike since my mid-twenties. Needed to find a way to 'exercise' to control heart/cholesterol/weight; have never been able to "work out" for the sake of health/working out, so had to find something I loved doing which incidentally had the desired results: cycling are it!! Never been a 'joiner' (not anti-social, just don't like oxymoronic 'organized fun'), and love to/prefer to ride alone because the rest of my life (family, work) is inherently social.

"Are you so hopelessly addicted that you can't imagine your life without bicycle commuting?"
Yep! Like another poster above, I get off the bike during ice-time (typically January/February), but otherwise use it for everything I can -- commute, coffee run, etc etc. Hate the car save when necessary, so use public transport during ice-time (or hitch ride with wife).

"Do you plan activities so that you can include a bike ride?" Absolutely.

"Are you ever late somewhere because you wanted to ride, even though you could have driven?"
Been there/done that; getting better (as cycling experience increases) at judging timing.

"Have you ever gotten off early from work to get in a bike ride before an appointment?"
Frequently! I'm really fortunate, as a university lecturer, to have minimal fixed hours, so I'm able to pile up a lot of miles 'extending' my commute/other rides when possible.

"Been to the doctor's in sweaty clothes?" Absolutely, though I do usually ride in decent quality, and clean (i.e. I rotate shorts/jerseys) cycling-specific clothing, so (I hope) I'm never too rank on any one day! Dentist appts. too.

"Suffered uncomfortable weather so that you could ride, and you'd do it again in a hearbeat?" Yep, apart from 'ice-time' as above.

"Give people a confused look when they ask you, "Are you going to ride today?" As someone said above, they've given up on me!

"Ridden a junk bike because that's all you had at the moment? Built a "Frankenbike" when your preferred ride was broken down and you didn't have the cash to fix it, just to feed your addiction?" Nope; have just the one, pretty good and constantly-being-upgraded bike; hence, yes to "Stayed up way too late at night fixing your bike so you could ride tomorrow, or to put on a new part that took longer than you thought it would take?"

To what lengths have you gone to ride when obstacles got in your way?
Whatever it takes, short of outright lies