Most big rig shops sell test strips.   They come in a little bottle.  Just like a test kit for a pool.  Dip it in the antifreeze, let it change color and compare it to the readings on the side of the bottle.   It'll tell you how acidic  the antifreeze is.   Usually 50 strips in a bottle.   More than I'll probably use in my lifetime.  

"How long do you think it takes for the coolant to lose it effective properties ?"

In a properly maintained system using GREEN COOLANT, every two years flush and fill with a 50/50 mixture.          

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1 year,but there is a tester you can buy that will tell one the conditioner is depleted.  the front cover showed is probably eaten out where the water splits to each bank.. the other spot is the therm aria in the intake manifold.. we never see this hear as any of the cars hear that are running will have any freez, if just for storage.. fortunately Y s had lots of cast iron and could stand lots of cavitation

How long do you think it takes for the coolant to lose it effective properties ?

I think (occasionally) that diesel engine coolant cavitation and coolant electrolysis are getting confused here. The damage shown on the front cover is from coolant corrosion, it's not being serviced on a needed schedule. The coolant goes acidic (anti-corrosion package becomes nill) and carries resulting sediments blasting away at wherever coolant flow is diverted,

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if you are not using antifreeze year around, then go to a truck repair and they will sell you a additive that will eliminate cavitation damage,or go to cummins or cat dealer. diesel engines ,as they live longer need additives even with antifreeze. the front cover i spoke of while back was not from a bird.,as well you will find cylender wall erosion when you rebuild and run into water at rebore.

This article shows a casting flaw found in some timing chain covers and suggest how to correct it.

NO  FOR ROLLER CAMS AND LOW SULPHER DEISEL

it's useable but the detergent package in diesel oils may be too harsh for gasoline engines over the long term. I used it for a couple of change cycles in my '55 Merc. It turned black very quickly so I'm guessing it broke down a lot of deposits. Another thing to consider is diesel oil formulations have changed recently to accommodate the use of emission controls found on modern diesels, including catalytic converters. The amount of zinc and phosphorus has been reduced just as in gas engine oils. Flat tappet engines like y-blocks need a pretty high zinc/phosphorus content. I think our moderator may be of similar opinion. Hopefully he'll chime in on this.

The last line of the last post" Rotella t is good for modern Diesel engines" is it also good for 1956 y blocks ? Forgive my ignorance