The items casting issue was always a troublesome one and our ruling on it came down to the fun factor really.
My outlook (and many of our group) is that many of them, as cast by a player (not an item) are reactionary in intent. Like when you attack a highly trained Martial Artist their reaction will be different than your average person... they will likely defend themselves in a much more effective manner due to their training. So, to some degree, we apply this logic to instants. Someone fires an arrow at you, and you see it happen, you can 'react' with deflections. Same would go for Landing and the like. Other instants you do in preparation for something, like an attack or haste, etc, so they are not much of a concern. Then you'll run into the exceptions (there are ALWAYS exceptions) like Absolution.
However, this logic doesn't carry over very well to items. Because you have an item that can cast deflections doesn't suddenly train you to the point that you could activate it as a natural reaction. This is where making an item take 75% makes sense. But is it actually necessary for balance reasons? Depends on the GM/Gamer. Like I always say when it comes to game design... Fun. Balance. Realism. In that order. If it's not fun, why play. If it's not balanced people will become frustrated. So if one of those things is put in jeopardy by insisting on 'realism' then you're creating a bad rule.
We've also ruled in some situations you pay for an action after taking it and may have to cancel your current action to do it... but, again, this logic doesn't apply very well to items.
So we just decided when it came to items the rule is however the spell was built into the item is how the spell comes out of the item. This effectively lets the GM determine how they want it to work in that particular case/item. It also lets you do things like say "This is a belt of landing. When you, as a player, experience or think you are experiencing an unexpected fall that will cause you harm, it is triggered.". The player is able to count on it when they need to, but they do not have control over it. The drawback is there are times when a character might THINK they need it and trigger it, possibly using up that 'charge' (for the round, day, whatever).