One might speculate the 24 has similar power handling as the HST which IIRC is about 2500W on the long term test on data bass. In my view this power level is going to fry the driver long term (8 hours) based on the power compression sweeps.
That said real world usage is not as extreme thermally, particularly with movie usage. My view is that if one were going to hammer these for a concert you would want to stay at 750W max per driver for the HST and I believe the 24 should be similar.
For HT usage or short term usage you could put a lot more power into them, 3000W seems fine for "peaks" during a movie where the bass comes and goes and is not constant like music allowing the coil to cool down during the parts which have a lot of dialogue.
A very old rule of thumb about how much power to supply is the old 2x the RMS/AES rating which typically is a good bet for most content as long as someone knows what they are doing and avoids clipping the system.
As a side note, one should always look at the compression sweeps on data bass to better understand the power capabilities of a driver. In all honesty Nick is a smart guy, if one were to do some math and look at the maximal power sweep with relatively low compression (about 1db) for the HST then they would see it is the 63.3V sweep and that works out to about 750W, if you double it as is conventional wisdom considering the crest factor of most program material you arrive at 1500W which is its official power rating. Nick has done exactly what any sane manufacturer would do and speced the driver within a reasonable power limit that is actually quite logical and not understated.
In my view the 1500W rating is spot on if one wants to have a system that is safe and will last for a long time, not only that but the system will remain fairly linear.
In this light it is usually better to have 2 "lesser" drivers than one "super" driver from a performance standpoint.