Having inspected several with very high mileage, I would rate those things as being quite durable.
Those small cracks you describe do not seem significant when you pull the mounts out and look at them closely.
In order for the halves to actually strike each other, I would expect the visual condition would have to be much worse than that.

On the other hand, they are not particularly expensive or tough to replace.

$.02

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1986 300E 5-Speed 240k mi.