This post does not encourage you to improper shutdown your system from now on , but a discussion in to the technical aspects of the impact of the improper shut down on the life of your hard disk. Please continue to properly shut down your system for maintaining your production environment systems
it is true that improper shut down can have negative impact for your operating system As there is a chance of file system corruption .
But it has nothing to do with the life of your hard disk.
You do a graceful shut down or just Pulled the wire , it is not a real issue for your present day hard disks. When the power is disconnected , the hard disk head is automatically moved to the Landing zone and it has nothing to do with your operating system
So improper shutdowns will not harm your hard disk
Still it is not wise to shut down your system improperly as your file system crash will cause
Data corruption and data loss