The original Infinity would run 30-40 hours (41 hours was the manufacturer claim) on an aa alkaline, with some reports that it would run 100 hours on an L91 lithium primary. The Infinity Ultra was more like
20 hours
The CMG Infinity's were my original white LED lights, and I still have several around in my emergency kits because of the long runtime they offer. With the move to ever brighter lights, runtime often got left behind, but there are quite a few multilevel lights available that offer greater efficiency on low than those original Infinity's. A couple of examples:
Zebralight H50 - Runs 3.5 days on low (manufacturers specs), and that low is brighter than the regular Infinity, but not quite as bright as the Ultra. I haven't personally tested the runtime on low, but the medium was spot on, so I have no reason to doubt it.
4Sevens Quark AA - Per this test,
Quark AA Runtime , it runs over 50 hours on low, and over 300 hours on moon mode, on a 2000mAh rechargeable battery. At such low drain levels the alkaline runtime should be significantly longer. Moon mode on this light is dimmer than the regular Infinity, and low is a little brighter than the Infinity Ultra.
Now I'm not trying to say that these lights are successors to the Infinity, but to the original question about runtime, yes, some of the current single AA lights exceed the original Infinity and Infinity Ultra in terms of runtime while producing comparable light output.