That is a long list and depends on the kind of work you're doing.
For me, if I might need it, I have two; and, if I usually need it, at least six. For example, I have two of each double pole breaker up to 40 amps, and six of each 15 amp. Driving for parts wastes too much time.
With my current employer, I built the stock up over two years, so it wasn't a big expense at one time.
Re: material stock#154870 11/22/0411:09 PM11/22/0411:09 PM
We do service work and remodel work. Our vans have a 10 page list of stock materials with everything from switches, receptacles, dimmers and cover plates in every concivable color, style or combination to ballasts to breakers to fan braces and device boxes, etc. Our vans are so well stocked the supply house calls us to see if we have an odd device. And we have back stock for all of these things in the shop. We make a lot more money with our guys working on the jobs instead of driving to the supply house.