When we purify water we only remove adventitious defilements from that water. The natural result is pure water. We do not produce, make, fabricate the water. And defilements never really mix with water, otherwise they could not be removed.
I belief purifying mind works the same way. The natural result of (permanently) removing adventitious defilements is Nibbana. Nibbana is not made, not created, not produced during this process. It is just the nature of mind without any adventitious defilement.
Another metaphor is the sun and clouds. When the clouds disappear the sun appears, but the sun was always there. It is wrong to belief the sun is created while clouds disappear. Likewise Nibbana.
Mind without defilement is unburdened.
If Nibbana was created due to the eightfold path or some practise it would be conditioned. It is not. It is in no way made, produced, fabricated.
The fact there is an umade, unbecome, unborn, undying is, i belief, the stable element in ourselves. I belief in the end there is no difference between ourselves and Nibbana. This does not mean Nibbana must be seen as mine or me.
The idea that an “I” experiences or attains Nibbana is due to kilesa, asmi mana. It is not true.
So, i think, stability is real.