Does it matter when I repair?

While playing through the higher difficulties levels, I find myself dying a whole lot (and therefore spending a whole lot of gold repairing my equipment). On death, it says that 10% durability is lost. Is that 10% of the remaining durability, or 10% of the original durability? If it's the former, I would think it would make sense to wait until my equipment breaks to repair. If it's the latter, I wouldn't think it matters.

Does the formula for calculating the cost of repairs linearly scale with how much durability is lost? If so, that might break such a tie.

It's 10% of the original, maximum durability.

Additionally, since the cost of repairs scales linearly with durability loss, and since item condition is a binary (either an item is broken, and contributes no stats, or it's not, and contributes all stats), it does not matter when you repair, so long as you do so before the first item hits 0.