My experience is that you NEVER is satisfied with rendering times, the first times I rendered pictures I didt it on a 14Mhz 68020, that ws slow, today with 2.4Ghz C2D its still slow.. When the CPU/FPU is getting faster, you always tend to add other things, like resolution or effects, or just complexity.

The scene I rendered yesterday in DS took ~2h, at least thats better than 42h wich I think is the worst I have done yet (many years ago..)