For what it's worth, my experience also echoes what Thomas is saying here. When he speaks of larger firms pulling shenanigans around doubling up work or other suboptimal practices...yeah, that's my company.
The only thing we ever billed at an hourly rate was forensic work, and that was specifically done to make up for the reactive nature of that work.
For everything else, it's a fixed rate contract based on the estimated number of person/weeks of work with a clearly defined scope as to what is expected to be done. Our contracting department (which itself is larger than most of the companies we work for) would never want to deal with anything else.
The only thing we ever billed at an hourly rate was forensic work, and that was specifically done to make up for the reactive nature of that work.
For everything else, it's a fixed rate contract based on the estimated number of person/weeks of work with a clearly defined scope as to what is expected to be done. Our contracting department (which itself is larger than most of the companies we work for) would never want to deal with anything else.