@anamur-- I'm doing this right now. It's been three weeks. The wart is getting smaller and it doesn't appear that there will be a scar.
I have noticed that the area has become really red though, so I actually took two days off from the duct tape. The redness went away and I've applied it again now. It is almost gone and it hasn't been one month yet.
The other thing is that after the first six days, the skin around the wart was irritated. But that was my mistake because I cut the duct tape too large. My experience has been that if you cut it just right so that it fits over the wart perfectly, it works best.