Hardening sprint and velocity chart

[Sandhya Paranjpe]

The team is thinking of having a hardening sprint of 1 week after every 3 sprints (each sprint of 2 weeks). So, basically a release would comprise of such milestones (3 Sprints + 1 Hardening Sprint).
This way, the team will get sufficient time to have regression testing, code clean-up etc. after every 3 sprints and we can avoid backlog getting piling up.
Is this a standard idea across industry?
I am also concerned about the velocity chart. The hardening sprint activities won't have any story points. If at all we use story points for these tasks, then also the duration of hardening sprint is of only 1 week.
So, should only the Jira Board query (to exclude these hardening sprints) sufficient to have a correct velocity chart?
Any other suggestion?

[Randy]

If you need to address technical debt/quality issues, do what you need to.

With that said, it might be worth investigating why this tech debt is accumulating and if there's any way you can implement product enhancements while maintaining quality and clean code as you go. 

[Sandhya Paranjpe]

Thanks Randy-Ho.

The idea of 1 week hardening sprint after every 3 sprints is as I have mentioned to have regression testing and also to address technical debt if any (in terms of design documentation, code clean-up etc.).

Yes, it is definitely good point to study why techinical debt is acuumulating. 

[Sandhya Paranjpe]

I need to know:

Is it a common industry practice to have milestone cycles of '3 sprints (each of 2 weeks) and 1 hardening sprint (of 1 week)' ?

If we do so, how to take 1 week hardening sprint's cognizance in the velocity chart and version report?

[Randy]

I'm sure there are teams that have hardening sprints every few sprints.  Whether you should do it for your team really depends on the context of your team, product, end-user, and goals.  

You should be asking yourself what the cost/benefits are of only being able to release every 4 sprints - i assume the hardening sprint is required to bring the quality up to a releasable state.  

In regards to your velocity tracking.  Consider what are you using the velocity chart and version report for?  How will including or excluding hardening work affect your use of these reports?