I am going to carry it 24/7...I feel more secure and prepared...especially at night. I drive new or newer cars because I never want to breakdown....especially on a highway...sidewall failure or puncture/hole greater than 1/4" cannot be fixed with the baby compressor and tire goo under the front seat. Do I want to be helpless if I get a flat?...road service is not going to bring you a new tire and get you on your way...they will tow you to a hotel and ruin your trip. Unless you don't mind being stranded not wanting a spare tire to me is inconceivable.
Just got my C-Max 2 days ago...replacing my 2010 Honda Insight that I will sell. I have got 2 flats with the Honda...one was a metal stake through the sidewall. No patch kit would have been able to repair that tire...if I was on the road after the tire stores are closed I would have been stranded....Luckily the Honda comes with a spare tire.
This ebay seller has 45 spares with wheels and they fit the C-Max---I purchased one, received it yesterday and put it on this morning with no problem. http://www.ebay.com/itm/221192273948?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649