I like the idea of spell components not mattering until they do. Like it's been said, having to keep track of them all the time is sort of tedious and boring. But, I think there are times where suddenly lacking them can create interesting narratives or challenges for pcs.

There are two ways I like to make this happen. First is the normal rule where certain material with a higher gold expense to them are the only ones that must be explicitly bought. And the second is more homebrew, but I make it so every caster natural get a wonderous item: the bag of eschew materials. This item is what supplies them with an endless amount of mundane or substitute materials for their spells. It's easily replaceable and basically weightless.

But, because it is an item, if your party happens to be stolen from, you're imprisoned, or a smart town guard at the entrance of a no weapons town takes it, then for that section of the campaign specifically you may need to problem solve how you'll cast your spells. Obviously depends on your players though.