IMO, you should attempt to cut weight at least once every 1-2 months just so you're
A) Familiar with the practice
B) You know your body and where you're at
C) It'll motivate you not to stray too far out of your weight class
D) You know how much muscle you can gain, and how much fat you need to lose to optimize your body composition
That said, Kroc's method is sound. OBVIOUSLY if you're lower bodyweight you're not going to be losing as much in poundage but you will lose the same proportionally. To tell you the truth Kroc's method works like a charm actually... I've heard a lot of variations of it (one including 1/3 rubbing alchohol in the water to suck more water out of your skin, kinda crazy, imo). Unfortunately, I think that losing more than 20% of your bodyweight in water weight (and for the combat athlete I'd try to stay within 10-15%) can have negative effects on your ability to perform optimally.
What I say here is NOT a knock against Kroc, power lifters, or any strength athlete. But fact is that MMA is NOT a "strength" sport (per-say) it requires EVERY type of strength, mental resiliency, and physical energy system the body utilizes. While you do get a 1 minute rest between rounds it's essentially 15-25minutes of Tabata intervals with a more unexpected (often times even moreso) vigorous pace, physical punishment (if not the end of the fight) everytime you fail, a ton of isometric work (something I never really see trained in MMA specials- but extremely important for submission specialists) and I'm not even mentioning how the constant movement factor will tax you aerobically... And different aspects of this are magnified depending on your weight class, your personal style of fighting and even bodytype.
The metabolic effects are much more like running a 5k than it is a powerlifting competition. Kroc is a fucking beast, but I seriously doubt even he would cut weight like that if he had to do what most combat athletes have to. The day before drop 30lbs, get little sleep (he said 3 hrs) and then trying to gain your water weight back and get rested again before a huge fight?
(most) People do it but a large majority of them having been doing it most of their life... and once again, it's something you have to practice to really perfect. When you know you've practiced a 15lb drop, and you're actually weighing less (after fight camp) than you did when you practiced the drop, you go in there with confidence knowing how your body will react. That alone is worth it's weight in GOLD. People forget the mental aspect.
How do 5k runners and athletes eat/train before a race? They get as low weight as they can prior to their event, then they carb load like a motherfucker. So they have energy stores and glycogen high as fuck before their event. That's what MMA athletes should utilize (to a lesser extent of course) but getting as low as you can in fight camp (using whatever substances you can that aren't banned of course) and cut the rest (enough to keep you close enough to a healthy comfortable weight and close to your opponent so that you're not completely outweighed (unless you feel you can (EASILY) make up for the deficit with skill/strength) and then carb load like a motherfucker before your fight, super hydrating your body (Finibars are great for this actually, they contain glycerin which will superhydrate your muscles, the effect is fairly short lived useful).
Forgive me for mentally vomiting all over this thread I had a lot on my mind regarding this in my own training, I'm going to do a practice cut at the end of summer after I bulk up a bit. I had to stop training for a little bit... life's getting in the way lately.