Just wondering, how long do you guys wait after clearing NVRAM(WPS+power on) in the end of the flash procedure, before setting up the router? I usually wait 5 minutes but, for example, dd-wrt recommends 10-15 minutes.
DD-WRT tries to write instructions that work for both newest high-end routers as well as very old routers with pretty weak CPUs. That's why they recommend such long waits, so even older routers will have a chance to finish initializing. It probably also takes into account some routers where they actually erase the whole nvram partition and are using very slow NAND I suppose.
With the RT-N66U/RT-AC66U the clear through WPS process takes only a few seconds, after which the router will boot normally.