Everybody has different strengths and weaknesses. I’m an avid cyclist, but just because you tell me I should be able to win the Tour de France because some other cyclists have done so, doesn’t mean I could win the Tour de France!
The Rule of St. Benedict is full of making allowances for the weak, but also encouraging the strong.
Living a conjugal life of, say, 20 years doesn’t mean that they can stop just like that, just because Abyssinia says that because other couples can do it, they can do it.
Other couples can be held as an example of course. And the couple that has difficulty stopping should certainly be taught that stopping would be preferable. But they shouldn’t be cut off from God’s mercy if they, at this point in their lives, are unable to. Of course no human has the ability or authority to cut anyone off from God’s mercy. The Church can suggest what she thinks is the best path towards it, and she can lead and encourage, but she must also always accompany even those who fail and reassure the couple that God is merciful and loves them.
Monks take a lifetime to reach their ideal of Christian perfection. It’s not much different for the rest of us.