As a retired mechanical engineer with many years in maintenance and a father and grandfather who were also tinkerers and love it. I have 24 as I have room for them with a right sized shop (see below). I rescue and sometime donates through a friend fine old bikes. I have bikes for my kids and their family about 6 and many I shuffle through. I usually have 3 or 4 waiting on maintenance or parts for adjustment to the ride (I am now 73 and things change), higher bars, shorter bar drops like 120mm, larger tires if possible, even my saddle preference has shifted a little.
Right sized shop