Andy_K 

But what happens when you figure out a more efficient way to store your bikes?

I used to have seven bikes hanging along the wall in my garage that my wife and I agreed would be allotted to bike storage. These bikes pretty much filled the wall, and I felt like if I wanted to get a new bike I'd need to sell one of the others. Then last winter my wife asked if I would make room for her to store her newly purchased Harley on the bike side of the garage. I found a way to do it without having to sell any bikes. Shortly afterward she finally admitted she was never going to fix up the old Dodge Charger that was filling the other side of the garage, so we found a new home for that and she got that side of the garage for her Harley. Now I have 14 bikes.

This may see far afield of the original question, but I think it actually answers it. I have a house in the suburbs with a big garage. This alone leads to possessing an enormous amount of "stuff." Would I be happier with fewer things? Maybe. Probably. Almost certainly. But the bikes are no where near where I'd start.

If you live in a small apartment in the city and have already trimmed the fat from the rest of your life, by all means sell all but one bike. But that bike will have to be extremely versatile, entirely reliable and above all the bike itself will need to be simple enough for you to maintain without worries.

But if you live in a simple house in the country and have a good shed in the yard, why not own a couple of bikes? As others have noted, owning a second bike does avoid some very real problems.