I`m using router Asus RT-N11P many years with openwrt. Starting from the 21.02 firmware, I noticed that the boot time has increased from 30s to 45s. After upgrading to the version 22.03 boot time increase even more, to 1 minute. This is definitely not ok for me. Is it possible to return 30s somehow???
I agree with @slh. Newer hardware will probably have a boot time that is significantly lower based on all of the factors -- more RAM, faster processor, and higher internal bandwidth on the memory and flash storage.
That said, the other thing is that routers running OpenWrt should not require reboots frequently in most situations. So if you're rebooting enough for the extra overhead of a reboot to be material in your usage, you may want to consider why you're rebooting as frequently as you are.
Boot times -within reason- don't really depend that much on the CPU performance, other factors (bootloader, time needed for RAM training and device initialization etc.) are the dominant factors (and these may even take longer on newer systems, more complex hardware, driving the RAM harder, more hardware to initialize). 45s are completely within normal expectations, anything under 60s isn't really a problem - and the 5 GHz WLAN will take another minute on top to scan the environment for DFS events as well.
Compared to many commercial firmwares (with proprietary wireless drivers, needing special orchestration, starting lots of proprietary (cloud-)dæmons, etc.), OpenWrt tends to (re-)boot significantly faster as well.
Minimum system requirements on OpenWrt however are usually specified very conservatively, only raised well after the fact of these no longer being viable for 'normal' operations; 128 MB RAM really should be considered the minimum sane requirement (combined with at least 16 MB flash) - and both are welcome to exceed those minima.