MOVs do not "absorb" energy, they are not energy sponges, they are in fact voltage dependent switches connected to ground. When activated they form a simple voltage divider with your equipment on one side and the the ground path on the other. The lower the impedance of the ground path the more effect they are. Part of the materials fuse inside every time they cross the voltage threshold but they do not dissipate any significant amount of energy on their own.

They also do not have a "shelf life" they do not degrade over time on their own. They are worn down by activation and more energy they pass the more they are damaged. They are expendable. Which is why it is good to replace them on a schedule and not to depend on the little indicator light, typically triggered by a fuse, to tell you it is used up.

Also the grounding system is very much vital to most, but not all, power conditioning systems. These are more or less dependent on a ground system of some sort. Most need a least a nominal ground system to work at all and ultimately use the ground system to discharge and as reference.

Such conditioning systems that operate partly independent of a ground are pretty common in areas where soil conditions make earth grounding difficult. Sand hills and areas with non-porous rock, particularly if the climate is very dry, can be problematic to effectively ground.

Many of those systems are large, heavy and expensive. Pretty much beyond the scope of what people are likely to install. People are not going to install even a relatively cheap $5000 conditioning system in their house. On the other hand, assuming earth grounding is possible and the system is solid a $100 whole-house surge arrestor can provide a measure of protection. And if combined with a $60 plug-in surge arrestor it can go a long way toward protecting your $1000 computer or $3000 home entertainment system. Most quality surge suppressors have an array of chokes, coils and capacitors to help smooth the passed waveform so the functions are not mutually exclusive.

Nothing likely to be installed by a homeowner is going make much difference with a direct lightning strike. But even a moderately priced surge arrestor array can help with the much more common small spikes from distant strikes, POCO switching, and noise from neighboring equipment sharing the transformer.

Note that a whole-house surge protector is covered in the NEC under "Article 285 - Transient Voltage Surge Suppressors: TVSSs"

And yes, the NEC, at least for "rod and pipe electrodes", does mandate the 25 ohm resistance as the dividing point between using one or two grounding electrodes. It mandates that if you cannot meet a 25 ohm standard with one electrode it "shall be augmented by one additional electrode". (NEC 250.56) Note that it does not specify what the resulting resistance might be.

The other grounding methods, such as a concrete encases electrode, are assumed to be at least as effective as two ground rods 6' apart. Reference NEC 250.50 for further information. We pretty commonly drive one or more well pipes down to ground water to meet engineering specifications.

I'm looking at a 2005 edition, what I have immediately available, but suspect this hasn't changed in the current edition.