That is a Mac Pro user attitude, and there is something to be said for it.
No it isn't. There are no large body of Mac mini users wishing their machines would crap out in 2-3 years. It is isn't specific to the Mac Pro or some "special category" of Mac users.
It is not even Apple attitude since their standard "Vintage/Obsolote" policy gives you 5 years after the product is discontinued coverage on parts/support. If the products are refreshed about every 12 months that's approximately 6 years standard on
every Mac. (for those at beginning of cycle. End of cycle folk run risk on last year of getting off.)
A machine that lasts 6 years is DEPENDABLE.
Being dependable for 6 year isn't the point. Having a workload
stuck at the approximately the same level it was 6 years ago is. Not only are these folks happy but the performance is "good enough" too. They are not bumping into limits.
The majority of Mac Pro users workload's are not growing as fast as the abilities of the Mac Pro is improving then it is a doomed product category. The number of users buying each will shrink. Folks will either move to cheaper product categories ( iMac or mini Tower Win/Linux boxes ) or just squat in their firewalled cave with a stagnant OS/Apps/Hardware.
Let's say there are 1M Mac Pro class users. (I'm being generous for round numbers and simple math. Somewhere are around 1% of the Mac base. ).
Let's say folks bought relatively evenly on 7 year cycles. That would put about 143K per year in the position of needing new hardware. Let's say 13% drop out each year to lower tier machines and 3% come in from bigger boxes. So a net drop off of 10% per year.
year 1 143K
year 2 129K
year 3 117K
year 4 106K
year 5 96K
In contrast if folks upgrade every 5 years but the inflow/outflow mix is different get a different picture. Starts at same 1M but the drop out rate is 5% and inflow is 3% so that net drop off is 2% per year.
year 1 200K
year 2 196K
year 3 192K
year 4 188K
year 5 184K
The first scenario Apple is going to dump. The second is a bit more tolerable but still has major problems inside of a high growth company. It is fixable with perhaps some product tweak to put where they might able to take that year to year transition positive.
The major problem is that the other Mac products look like the inverse order of the first scenario. Their numbers are going up; not down.
The problem is the longer cycle people hold on a single product the more folks are needed to make it show growth year over year. If the other mac products rotate on 5 year cycles and the Mac Pro on 7-8 year cycles then needs a bigger base (which it clearly doesn't have) to show growth.
People whose workloads are steadily increasing at a significant rate aren't on 6-7 year cycles. Every 5 years Intel/AMD (and other component vendors) following Moore Law typically will have doubled the performance (with triple the transistors). That's a curse if the workload isn't only increasing at 2-10% per year or a blessing if the workload is doubling every 5.
This means we can use it for
work, and not worry about it breaking in the middle of a job. I will pay extra for that
Actually, I think most folks would characterize it as paying extra to be able to 'pop' the hood, swap out HDD/card, and keep going.
The solution where the parts don't fail for 6 years just points at solutions like mini and iMac all the more. If they don't fail then don't need to open the box.
Just dreaming really! 
