You guys are way "over thinking "all this. Air cleaners DO NOT need to be cleaned till encrusted w/ at least 3/8" of dandelion lint. Deck tops do not need to be cleaned until the build up is so thick you can't get the deck to latch in the up position. (Or there are more than 2 mice living in there) And, the underside of the deck absolutely NEVER needs scraping. I know all these things from yrs of working sales at a jd dealership. You wouldn't believe the mowers we got in from dairy farms where the lawn mower was THE LAST machine to be serviced.
Those old jd lawn tractors w/the Kawasaki single cyl engines stood up to amazing abuse in their day...I mean...truly amazing.
Well yes & no.
Cows are not real fusssy about the quality of the cut just so long as the weeds they do not want to eat are gone so the grass they like to eat can grow.
You usually mow after the cows have been in the paddock so there is not much grass to cut the first place and usually you mow a paddock at 4" to 6" because you want to leave a lot of grass behind to get maximum growth.
The farmers would be running their mowers in a year what the commercial lawn care opertors do in a month.
So fuel usage is not a big problem neither is downtime, you can always do it next week, not so with paid for mowing or worse mowing with a team that is costing you $ 100 + per hour , mowing at 1/2 the optimum speed because the mower is not running properly.
All old mower took a beating
I still use daily mowers that are 60 years old and customers are amazed that a 60 year old mower does such a good job, they just take longer because hydro boxes, gear change on the fly, elecric PTO, & diffs were not to appear for another 20 years.
I heve even sold a few 40 year old mowers because the customers liked them better than their current 10 year old mower and actually found them quicker & easier to use.
The old 8/24 to 10/30 were the optimum size for blocks of 1 acre or less, and you just can't kill them.
In particular the RER's are excellent and represent the optimum mower lay out for durability and reliability.
So yes they will run, and for home owners it will not be much of a problem but they won't run giid enough to make money with.
As for deck buildups, JD use a lot of steel spindle housings which do not rust / or rot as fast as he modern alloy ones.
JD decks do not run controlled ventilation so do not need to be able to draw air down the spindle housing.
However they do burn and I see at least 1 mower fire every season caused by belts running on dry grass built up under decks.
So horses for courses and the boys are not "over thinking"
Keeping any piece of equiptment clean is always a good idea however in some circumstances it is not as high on the priority list.