I like the way planning poker works at the beginning of any project, letting you compare and discuss details of each story with one another.
One of the issues I've noticed with this is that through time and as you gain more experience with the problem domain, you tend to vote less points for each story, i. e., a story that was worth a 5 or an 8 at the beginning of the project might now be worth a 3.
How do you avoid or tackle this problem in the best possible way?
Is there a better way to estimate?
Should the stories always remain the same, or is this story points decrease ok?
Best Answer
I don't think that's a big problem.
There are two obvious things that could be causing that. One is that you're experiencing some mild point deflation. The other is that your team is actually getting faster. (I hope it's the latter!)
Either way, it shouldn't be a big deal. The two main uses of velocity are figuring out how much work to take on in the next iteration, and making rough estimates of delivery dates for larger chunks of work. Neither of those is harmed by a gradually changing velocity. Indeed, if the improved velocity comes from getting better, then your new numbers present a truer picture of the team's capacity.
If the velocity is changing too quickly for comfort, then one response is canonical stories. Go through the last couple months, picking out 3 stories each to represent the point levels you use. Put 'em up on the wall where you do estimations. Then as you estimate, use them as comparison with the story you're dealing with. That should reduce both drift and volatility in your estimates.