My DS stove only has two 6" corrugated 90's and then about an 8" straight piece sticking into the thimble. That section has the MPD in it. The joint between the two 90's seems very tight, as is the joint between the second 90 and the straight section.
On my old setup with the Franco, I used the regular black pipe with two tees and one of those four-section "adjustable" 90s. The last couple times I put in new pipe, I cemented all the joints because I was concerned about draft loss. I figured I was already losing enough through my cheap baro damper, tees, and that adjustable 90 piece.
We have a mildly damp basement...no mold or mildew, but enough dampness to soak into any fly ash left in the stove or pipe and cause corrosion. In my early years of burning, I didn't remove the pipe from the thimble over the summer
and let me tell you, the humid air, along with outright dampness when it rained, were enough to rot my pipe over the summer. I wised up and started removing the pipe, cleaning it outside, and storing it in a dry place. I also started running a dehumidifier in the basement during the summer months.
Still, even with all that, my pipe wasn't lasting more than 4-5 years at the most. This corrugated stuff looks a bit heaver and, I hope, might last longer with care.