Magnetic media aren't worn out by repeatedly being written. (They can be adversely influenced by the read-write head lying at one particular location most of the time, whether active or not. The mechanism here is interaction between airflow and tiny amounts of contaminants within the sealed HDA. For this reason drive firmware periodically performs a random "elsewhere" seek on an idle disk)
The amount of power used in writing a track is a very tiny fraction of that used to keep the whole mechanical assembly spinning and to move the heads around.
So I wouldn't expect this aspect of SMR to reduce drive life expectancy.
However, there's a major qualitative change with SMR. In a conventional magnetic drive, once your track is written, it stays there on the disk without any maintenance being needed. With SMR, it will be read and rewritten whenever nearby data is updated. If something isn't working right, there is much greater potential for your pre-written data to become scrambled. In this respect, I'd expect SMR drives to "brick" themselves far more easily. More like an SSD (which also performs read-modify-rewrite cycles), less like the magnetic disks we're used to.
I hope that "old technology" drives remain on sale for a considerable overlap period!