A think that this discussion is a little biased. For one hand, the form of a thesis depends a lot on the field. The more theoretical, the more it can be concise, but in some fields you need a lot of experimental data.
Another issue is that most dissertations are not made from a single, ground breaking contribution, but from several incremental contributions and you need to integrate them into a coherent text.
I've not finished my dissertation, but it fall in the latter case and I think it will be some 100 pages long.
By the way, it will be interesting to see the length of the PhD thesis of the people that claims that "the length of a thesis is inversely correlated to its brilliance" (only cperciva declared it)
Another issue is that most dissertations are not made from a single, ground breaking contribution, but from several incremental contributions and you need to integrate them into a coherent text.
I've not finished my dissertation, but it fall in the latter case and I think it will be some 100 pages long.
By the way, it will be interesting to see the length of the PhD thesis of the people that claims that "the length of a thesis is inversely correlated to its brilliance" (only cperciva declared it)