How long ago was carlsbad caverns was formed?

A web-site devoted to the cave's geology(rozylowicz.com) gives passage inception in already-fractured Permian limestone, as 20-30MA, after uplift had advanced sufficiently for karst development to start.

I have also seen elsewhere an age of <4MA, but that was based on analysis of minerals in one area of the system.

I would though treat Rozy Lowicz's work with some caution because it implies the cave's large passages and chambers were formed by collapse, not dissolution. This cannot happen. Collapses fill caves, not form them. For breakdown to occur, there has to be a void for the weakened rock to collapse into; and in the active phase of the passage the stream erodes fallen rock away.

A karst cave passage can only be formed by a stream; but infilled by blockfall as percolation water attacks the rock surrounding the joints in the roof rock.

Far more likely the dry passages in Carlsbad Caverns are like those in any fossil cave (including a far more modest caveI am helping explore): the original streams have changed courses or disappeared altogether; and the dry passages are now decaying.