Mike Cohn said in a newsletter today, "I'm frequently asked if a team can pull an additional product backlog item into a sprint if things are going well and they are clearly going to finish everything early or have already finished everything early."
"They can also drop work if things are going poorly. "
"When a team plans a sprint, they are doing their best to determine how much they can finish. They won't be perfect every time. "
"I think we all know a team will need to drop work occasionally. But for a long time, I've been troubled by how frequently I'm asked if a team can bring more work into the sprint. The answer to that seems so obvious that I couldn't figure out why I was being asked that question so frequently. "
"So I started asking people why they were asking me. And I finally figured it out. Teams are afraid of bringing something into a sprint and not finishing it. "
"So let me be real clear about this: There is nothing wrong with being partially done with something at the end of a sprint. The problem is when a team is partially done with a lot of things. Or, worse, partially done with everything. "
"There is nothing wrong if a team finishes eight and a half product backlog items. I'd rather have them do that than stop after eight and refuse to start the ninth because they know they won't be able to finish it within the sprint. "
"So, avoid having multiple things unfinished. Finish one of those things instead. Be sure you have at least something done every sprint. But don't stop your team from starting on an additional item near the end of a sprint even if they know they can't finish. "
"I've written more about this on my blog, where I addressed the risk of letting unfinished work accumulate. If you want to read more, you'll find that here: https://www.