As silly as it is, I've "tested" the effectiveness of Naltrexone pills in a number of ways as part of planned relapses. I have found that no matter the amount I take (as little as 5-10mg, as much as 50-100mg) you can expect a bare minimum of 96 hours before you feel anything, much less the euphoria you are looking for in the first place. After 5 days or more you will begin to feel the effects fully again.
I have tested this timeline a few ways: after daily doses @ 50 and later @ 25mg, after a single 25mg dose to rapidly detox, etc. Doesn't seem to matter if you take one tablet or 100 in a row, if you want to get high again you'll be waiting at least 5 days. Didn't stop me from wasting plenty of cash on pills that didn't do a thing but make me groggy the next morning.
I suspect that the company claims only 24 hours blocking effects to incentivize you to buy more pills, but that may be the cynical skeptic in me talking. In my personal experience, there is no question that if you are limited in funds and/or naltrexone and still want to stay clean that you can take half a tablet every other day or even every 3 days and still retain the same blocking effects. I don't recommend it, because part of its effectiveness lies in consistent usage, but if it's a dire situation and your choice is either split your last couple of pills over the course of a week and stay clean, or take the last 2 and then get high a few days later, I think the choice should be fairly obvious.
This is truly a miraculous drug -- IF you're ready for it. Clearly I'm not done blowing thousands of dollars a week and ruining my personal relationships or I would be taking it more seriously.