Given that there is a recount only once in about 160 statewide elections, and given there is a presidential election once every four years, one would expect a recount about once in 640 years with the National Popular Vote. The actual probability of a close national election would be even less than that because recounts are less likely with larger pools of votes. 

The average change in the margin of victory as a result of a statewide recount was a mere 296 votes in a 10-year study of 2,884 elections. 

The common nationwide date for meeting of the Electoral College has been set by federal law as the first Monday after the second Wednesday in December. With both the current system and the National Popular Vote, all counting, recounting, and judicial proceedings must be conducted so as to reach a "final determination" prior to the meeting of the Electoral College in mid-December.