…so don't bother wasting your time savescumming it.
How shield numbers works by u/GoldenShadowGS :
If the shield number is higher than the weapon number, then parrying will disarm the enemy. If the shield number is lower than the enemy's weapon number, then a parry won't disarm them. There is also durability factor. Raw durability is an invisible value and has nothing to do with the displayed number. However blocking an attack from a weapon with a higher number than the shield will cause extra durability loss. I've tested this by giving a bokoblin different weapons and let it attack different shields. If the weapon number was lower than the shield number, the shield blocked the most number of hits before it broke. It doesn't matter if the weapon was power 2 or power 50 against a shield with a number of 54. It broke in the same number of hits. However, when the weapon number is greater than the shield, the shield starts to break is fewer hits, and it breaks in even less hits as the weapon number keeps increasing.
Going by this explanation, having a Guard number > 90 is pretty much useless. Why? Because except from those 1 or 2 Moblins in the Castle wielding a Royal Guard's Claymore – and even then, only if it rolls up with an atk+ modifier – there's not a single enemy in the entire game that can both be disarmed AND carries a weapon higher than 90 atk. Lynels, the only other enemies possibly carrying a > 90 weapon, can't be disarmed.
As for regular blocking, durability is also basically a non issue. First because, again, for this to matter you'd need enemies with weapons > 90 atk. Which means basically those aforementioned Moblins and Sword/Crusher Lynels (and again, rolling atk+ bonuses on their weapons). Second, because the Hylian Shield has 800 durability (which is about 13 times more durable than the next best option); who cares if a blocked hit from those rare monsters takes up a couple more durability points from it? It will still last you days.