Probably safe enough to leave it in. You will have a problem if you hit a read error on the bad drive while the array is degraded, or at the same position as a read error on another drive. So as long as the other drives hold up, you are fine. If another drive fails though, you will need to be very careful. Probably keep the array read-only until you are back with everything working.
Reshape is an inherently slow operation as is reads from the drive, then goes back and writes again. As such it is much slower than e.g. recovery which reads sequentially from some drives and writes sequentailly to the other. You'll just have to wait.
