Congrats on the GS status!
I am not sure it is a viable strategy for most, and I am always concerned when anyone relies on anything "lifetime" with United - They have carte blanche to change at any time.
But if you enjoy the travel, and the MRs became a hobby, there is nothing wrong with that at all. I travel a bunch and enjoy each trip. But at 1.1M lifetime, 4M is just a blur on the far-distant horizon.