Is this a world record?!
 

I was outputting a short film a month or so ago, and nearly fell off my chair when I saw the render time left that PPro2 was suggesting!
By the time I'd pulled out my stills camera to grab a shot - the numbers had plunged to a mere 363 hours!
I know my system is old, but surely it can't be that sloooooooow!

i understand
 

I was editing something on an old mac at the church, and I hit apple-r. I'm thinking the render time will be no more than an hour (it was a lot to render) ... I saw the number from across the room... "14 hours?" I thought. "That's too much!" Much to my surprise, I was wrong. My vision is bad, and it said, "About 14 DAYS!" DAYS! It was measuring in calendar days!! That's a half of a month!

The next day I convinced the church to buy a new computer

Much of this has to do with encountering tough spots in your timeline, those with many layers or heavy in effects, where the rendering practically grinds to a halt as the FX stack for each frame is processed. As soon as the render hits plain video or the easy stuff, the render speed picks up and the time is dynamically updated and it can be a huge difference.

If you have short spans of FX and the majority is straight cuts and video. You can simply test render a ten second spot of the average stuff and see how long it took to render. Then do the math based on the entire length of the piece for a better proximation. Then you'll know if it's a few hours vs. overnight.

the bottleneck effect.