I am a bit of a contrarian when it comes to streaming defenses. I feel like my team has enough playmakers and depth to the point where I am rostering 2 defenses and plan on using them ROS. I have the Colts and the Pats. The Patriots always get better as the season goes on, the Colts actually have a very solid defense when healthy. Both have playoff matchups I like.
I am 6-1 as of now, all alone in first, I have a good team with good depth. That is the only reason I am stashing defenses. I missed out on a couple nice pick ups because of doing this as well, but I feel like in the long run this will ultimately benefit my team. I did this a couple of years ago as well but later on. I am a huge fan of stashing defenses if you can clearly see where your team is going. If you are not totally confident I would not recommend stashing. I am also not stashing a defense for a specific week in the playoffs. I have 2 defenses that I am using ROS, not just the playoffs.
This has been such a difficult season for fantasy defenses, anything can happen. Matchups can look very different in just a matter of weeks too. Good luck.