I carry around 7 - 10 lenses in my bag almost all the time. I'm a Pentax shooter and the small size of the lenses they produce makes it possible to carry many optics in a small space. Typically I would always carry the '3 amigos' - the 31 f1.8, the 43 f1.9 and the 77 f1.8 and almost certainly the 'wedding pair' of 16-50 F2.8 and 50 -135 f2.8. then it depends on what I'm shooting. For street I may load the 15mm f4, 21mm f3.2 and 40mm f2.8 pancakes (these lenses can fit in a your pocket without a problem) for portraits I may also load the 55mm f1.4 and the 100mm macro. For landscapes I have a 12-24 f4 as well.
For those not familiar with the Pentax system, the first three lenses I mentioned are film era FF lenses, the others are designed for crop sensors; but it is thought that at least some of them will also work acceptably on a larger format sensor. We will find out for sure early next year
If were to count all those in my camera cupboard it would total over 50, but very few of these get to see any light these days. Occasionally I like to put an adapter on a body and shoot beautiful old screw mount Takumars just for the hell of it.