Technology always moves forward and drones are advancing the same way PCs were in the late '90s and well into the 2000's. You'd buy a bleeding-edge PC and it was out of date in two months.
The Inspire 1 was launched in November of 2014. If I recall, I got mine in May of 2015, or somewhere there about. I still use it almost weekly doing roof and chimney inspections. After all those hours if flight time I just had my first battery pack die from a bad cell. The rest are still going strong, as is the drone. I fly it because it's still useful and does the job. I can't tell you how many times over it has paid for itself.
My Phantom 2 Vision+ had a service life of about six months before being replaced. After two years in service, I still see no need to decommission my Inspire 1. In fact, I'm about to spend more on it in the form of the Z3 camera (for zoom capability) and possibly upgrade the propulsion system.