The Rolling Stones are known for classic, timeless hits ....

Hello, insead22. If we break down the sentence, we can appreciate that while the sentence may not appear any time soon on the GMAT™, it is functional, and it does contain parallel elements. First, classic, timeless hits is not an appositive. An appositive is a noun or phrase used to define or describe another noun, and both classic and timeless are adjectives modifying the same noun, hits. Rather, the construct is what is known as a coordinate adjective pair. The comma is used between the two adjectives to indicate that their order could just as easily be reversed while still modifying the same noun—timeless, classic hits is perfectly fine in spoken or written English. (Note that not all stacked adjectives are coordinate. For instance, in the sentence The big brown bear attacked the hikers, we could not reverse big and brown. Size words tend to precede color words.)

Moving on, the parallel elements are both nouns—selling out stadiums for their performances is a gerund, not a participial phrase. Element X is, essentially, hits, and Y is this gerund, at its heart selling out stadiums. Thus, the sentence fits the following form, with the coordinate adjective in blue and the parallel (noun) elements in pink:

The GMAT™ tends to favor strictly parallel elements to understood or implied parallelism, so, on the exam, I would expect a second for to precede the gerund: known for X and for Y.

Perhaps now the sentence makes more sense. Good luck with your studies.

- Andrew

The sentence could work as it is, but the addition of a second FOR will make the sentence more parallel and better.
This is what the sentence would become:
Another point, unrelated to parallelism, is that "Selling out stadiums FOR their performances" is not idiomatic. WITH will work better.

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