That amount of new machines sounds so crazy to me.
I am still running my iMac 2012 and the only reason i need to upgrade it is for Video work. I was looking into coding, so it would be sad Xcode would be gone with the next OS X Update (i think) - but that was more like a geek hobby and i still have my MacBookPro.
Added benefit to the new iMac will be that a new GPU should enable me to play Planet Zoo in a less than Playstation 2 look (but yes, that game runs perfectly fine on NVIDIA GeForce GT 650M 512 MB with low settings). But i would not buy a new iMac at 4000€ for that obviously. I would not even buy a 800€ gaming pc for that.
For Lightroom and my new SonyA7M3 this iMac 2012 actually works out better than my MacBook Pro 2015. The Retina just kills performance in Lightroom i think.
Before that i had one other iMac... it took it with me when i moved out of my parents house. My dad still uses the iMac he got back than (2008) when i took the old one... so what i took must have been a 2006 or 2007 model and i used it till 2012 when i just needed some extra power for Uni Design projects.
So this iMac we are waiting for right now will be my third in 14 years and at 4000€ it better make it to at least six years.
My MacBook (2008, first Aluminum one, only one without the Pro i think) i replaced nearly 9 years after i bought it. Granted, installing a SSD prolonged the life of that one massively, still was able to get 1/3 of the buying price when i sold it.
I got the 2015 on sale back than because i was not happy with no MagSave and all the USB-C Ports on the redesigned Model. Super happy with that decision because having the ports actually came in very handy on multiple occasions.
But yeah, thats
two MacBooks in 12 years and no intention in getting a new one any time soon.
(both 13 inch)
iPad is about the same, got the iPad 2 day one and replaced 2018 with the "consumer iPad". So thats 7 years. But in the end the iPad 2 would do pretty much nothing but play videos properly, just typing input on the keyboard would take seconds to finally show up on screen.
iPhone i am still running the original SE (only my second Smartphone, and fourth mobile Phone) and since i replaced the battery recently i don't feel a need to upgrade (even if it's probably falling of the Xcode Bandwaggon later this year sadly...)
Thats still a good amount of electronic wast for a lot of money. But still, three iMacs in 9 years just wow me.