To get true understanding of what you're working with you need to be able to trash the configuration of your gear at will. I learned a lot buying up some big old Cisco Catalysts and EMC Clariion SAN boxes back when I was doing data center work. Later on though, when I was in charge of buying new stuff I'd rack the stuff up first and go crazy with it before it was in production. Either way works. I don't miss having those fans running in my house though.