Opening weekend is nowhere near as bad as any hell night, that's straight up absurd. I've gone for both opening nights the past three years and I've never seen a house go up above 75 minutes - and that's always the Jaws queue house. Everything else remains peaked at 45 minutes.
That said, there are other factors to consider - scareactors are still learning the ropes, and the event closes at midnight instead of 2 AM. However, as pointed out above, the crowds tend to be tamer and more enthusiastic, and you have a greater chance of seeing experimental elements that could be cut by the second week of the event.