I'm sure this situation isn't exclusive to Microsoft. If you're valued as an employee and want to do something like this, make your wishes known to your management and see if they're willing to work with you. If you never ask, the answer is always no.
I work for a pretty small security company doing assessments (penetration testing, vulnerability research and stuff). I loved the job and really didn't want to lose it but was willing to.
The first year I asked, I basically just said, I love working here but I'm going to go hike this trail for 6 months and hopefully they'd work with me.
Then I asked for it again the next year, again willing to leave but didn't have to.
Finally, I took some time with my boss and had a discussion around continuing that work pattern into the future and how I can make it easier for them (notice periods, time of year to take off and such)
I completely agree with your last statement, if you never ask, the answer is always no. One of my coworkers when I returned the first time actually asked me how I asked because he wanted to do the PCT.
Once you're out of debt and have the savings: do it. It's generally easier to do these things before other responsibilities start having higher priorities.