I don't know how many years I would have gotten out of the mower but, my back wouldn't have taken the beating, our yard is so bumpy that I had been bucked out of the seat a few times on the tractor to the point where it activated the kill switch. The previous original owners did not have a finish grade done on the lawn so it's just as it was when it was a live stock farm back in the day so it's really rough.. The additional upside to the zero turn is a cut my mowing time from 2+ hours to roughly an hour, that time savings was worth it alone to upgrade the mower... I had mowed this lot for 2 years on the tractor, mowed at my last place's one acre lot for 3 years prior so I got a good 5 years out of it, paid $2k sold it for $1k, I guess I did OK... Paid close to $6k for the zero though so hopefully it will last me 15+ years...
To the OP:
Sorry for the off topic discussion, those drone pics look pretty sweet!! Nice yard man!