Even if you can't base usefulness on specific spoilage progress, you can definitely have too-hot-metal spoiling into just-right-metal spoiling into too-cold-metal. Bit multiplicative in terms of different item types needed, but possible.
Yes, it is almost always better to make different types of items for these kind of mechanics. Mainly because all of the game tools you have are design and work based on item types (inserter/splitter filters, the whole logistic system, train interrupts etc)