As far as I am concerned it just happens. But I let the computer check for updates automatically, so it normally happens the next day. It's a common experience that if you try to download patches or new versions of an OS the day they are released there are going to be delays. Pretty obvious, really.

Ive had it days/weeks after if ive been on holiday during patch Tuesday. Will check for updates a week or so after patch Tuesday and will take ages. Then for the rest of the month its quick

I just accept it now as the norm for this PC