I suspect that the cost/benefit isn't there. Those who need the "biggest Ultra" will be happy with the previous generation or so, and so they'll refresh that on a 2 or 3 year cycle.

Given that generation gains are not sufficient to make a Max twice as fast as the previous-gen Ultra, a longer cycle is rational. The M3 Ultra is still the fastest M-series system.

M5 Max outperforms M3 Ultra.

M3 Ultra, 3.3k single core 27k multicore on Geekbench. https://browser.geekbench.com/v6/cpu/16959045

M5 Max, 4.3k single core 29k multicore https://browser.geekbench.com/v6/cpu/16956481

Fair - one of the fastest. Still, if you need more memory, it’s the M3 Ultra.