We operate over 1000 switches in our data centers, and hardware failures that require a switch swap are common enough where the speed of swap starts to matter to some extent. We probably swap a switch or two a month.
having operated a network of over 2000 switches, where we would see maybe one die a year (and let me tell you, some of those switches were not in nice places...no data centre air handled clean rack spaces etc) this failure rate is very high and would certainly be a factor in vendor choice. for initial install, there are quicker ways of dealing with cage nut installs... but when a switch die in service, the mounting isnt a speed factor, its the cabling (and as others have said, the startup time of some modern switches, you can patch every cable back in before the thing has even booted these days). alan