it is not possible by selenium because I keep my sleep time 1 sec for the page to load fully. and @ddmrddrmr sends 1.2 merits per sec on average.
in middle of the spree i will get stopped because of internet connection or page will not load.
You should try headless browser in order to increase the speed. I'm not sure it's going to be the solution for you but you should at least give it a try. A few weeks ago I used some Selenium scripts via a headless browser and the speed was improved a lot with it.