Cathy and I held on to our Honda Insight for over a year making an effort to drive it every couple of weeks after we got the Roadster. In addition to the issue with the 12V battery, there's the problem with gas going bad, especially when it contains ethanol. We sold it a few weeks ago to a SEVA member who will put its 50+ MPG to good use.
We now have only the Roadster and a 2002 RAV4-EV.
While the Roadster has been very reliable, service can take a while. Our car spent a week in the shop while they figured out a problem that turned out to be the subwoofer amp. Other cars have spent over four weeks in service while a complex problem is tracked down, new parts ordered and shipped, then a deeper problem is found. Carl and Mark in the Seattle store are awesome, but they also have to cover a huge geographical area, so service gets slow when one is in Alaska while the other is in Idaho.
Anecdotally, at least half of the long service times are for non-warranty issues, car accidents or other vehicle damage not caused by a design or manufacturing problem.
Still, the problems that require long service time are rare, and the cost of keeping and maintaining a spare gas burner is high, it seems like it's a better bet to just plan to rent. Of course it would be nice if Tesla absorbed that risk and kept some loaner Priuses (or Leafs!) on hand for those rare situations.