I've had my Roadster for 2 1/2 years now. Since it pre-dates the Super Charger network (or any other network, for that matter), all I have is home, public / work, and an occasional destination site for charging. Never been a concern.
Last weekend was the first time I had the occasion to take the car beyond its 1-way range, to attend TMC Connect in Monterey. Just like the non-Tesla EV owners, I stressed a bit about where to charge along the way, and now long it would take. Did some homework ahead of the trip with PlugShare, and found a park-and-ride with charging and a convenient place to eat nearby. It took about an 1 1/2 hours to charge, most of which was accompanied by lunch, catching up on some email, and time to just sit and relax. Very restful, actually. More so than I had expected. Arrived at my destination with plenty in reserve, both in terms of range and spirit.
This is a tale that's been told a thousand times by others. I re-tell it here in the Model S forum as a reminder. The time taken to charge along the way is a gift in some ways. Super Charging is fantastic, but it doesn't cover every corner of the planet, and probably never will. Public charging will often get you to those slightly farther out-of-the-way spots where the 6-lanes don't go, and it can be a handy top-up during an otherwise hectic day of running around whatever is local to you at the time. It does matter "when you need it" (as stated earlier), and to the furthering of Tesla's mission it is essential. And sometimes it makes for a good excuse to stop and get a cup of coffee and recharge your own batteries.