That will be very hard to assess. As any natural product, this material can have defects in the form of voids, which are not visible, but can initiate breakage if loaded, usually during service. Stone dials are few and rare, so a watchmaker will surely remember if it cracked. But whether the aventurine cracks more often than malachite, which was also used by Omega? IMO no one will know, as you can just have 'bad luck' with yours. But there is surely a reason why the watch producers do not offer stone dials that often.