This wouldn't be efficient for a variety of reasons.
First off, since you get a flat amount of ip for a win + an amount for the game length, it's better to play a bunch of short games than a few long ones (same total time based ip, but you'd get the base flat amount more).
Second off, you get reduced ip in AI games after various level breakpoints, so you'd probably be better off cranking out a ton of pvp games, which are probably more fun (not to mention useful practice, as all the champs in the game won't do you much good if you play like a bronze 5).