Diablo – Are Nephalem Rifts endless

This Blizzard Post on the upcoming patch Aptly describes the hidden benefit of the Nephalem Valor buff and the changes coming to it. (It's roughly 1/5th of the way down the post, "The Nephalem Difference")

Ahhhh screw it, here's the quote:

"It’s no secret that our goal for the end-game item hunt is players hunting monsters packs, building to five stacks of Nephalem Valor, and then killing a boss. While we’re seeing a lot of that occurring, what we’re missing is people feeling like it’s worthwhile to continue onward after killing a boss. To help hit that goal we’re lowering the number of guaranteed Rare items on bosses when you have your full five stacks of Nephalem Valor from two guaranteed Rares to one guaranteed Rare (you still have a very good chance at multiple rares, it's just no longer guaranteed). In exchange, all champion and rare packs will now drop a bonus guaranteed Rare item when you have your full five stacks of Nephalem Valor. The change benefits players with more overall drops, and a reason to push to continue progressing."

With a recent hotfix, Rifts now have +25% Legendary drop rate so there is another huge incentive to going on Rift runs.

One benefit of doing bounties/Nephalem Rifts is the blood shards that you gamble with at Kadala. The Rift bosses drop pretty large chunks of them at a time so it makes it much easier to scratch the gambling itch.

Also, I'm not sure if it is due to Adventure Mode or because the Nephalem Rift itself, but mob density also seems to be a lot higher than your average area. The high density, of course, results in more experience/drops. There are a large number of champion and elite packs spread throughout the rift that you can continue to kill after the rift boss is dead as long as you don't speak to the Nephalem Spirit in town.

There are some unique aspects to the rifts themselves there are unique pylons that can greatly speed up your monster killing and looting:

• Shield - Impervious to damage for 30 seconds.
• Conduit - Lightning zaps your surroundings for 30 seconds.
• Power - All attacks do +400% damage for 30 seconds.
• Speed - Maximum run speed greatly increased for 30 seconds.
• Channeling - All resource costs and cooldowns are reduced

Finally, actually going to the rifts is the only way you will be able to unlock the Nephalem Rift achievements though as with all achievements your mileage can vary based on how you rank achievements.