I have discovered the secret formula for scoring a Plus Points upgrade on SFO-EWR - Here's what I did, just do the following and I bet it will work every time:

1. Book on a Saturday mid-day
2. Book a flight that is assigned to a 757-200, without true Polaris seats
3. Apply Plus Points
4. Get United to switch equipment to a 757-300 at T-72, making the first class seats even less valuable and adding 50% more first class seats
5. Voila!

Route: SFO-EWR
2. Date: 6/15
3. Fare Class: Q
4. Y->F
5. # of PlusPoints: 20
6. How many days/weeks in advance ticket was purchased: 41 days
7. How many hours/days/weeks before departure did upgrade clear: T-36.5