‘Lifespan’ - A new enchantment for tools and armour

We already have unbreaking and mending, but what if there was a third enchantment like them that, similar to how they will make your equipment last longer, can keep your tools from breaking? The idea of ‘lifespan’ is that it would be a rare enchantment for tools, weapons and armour that would not reduce the durability drain in any way when the tool is used, but instead would increase the standard durability of the tool/armour by 5-30% or so (still deciding) if its total. The different things you break or block against will still drain their standard amounts of durability, but the lifespan enchantment makes it so that the durability has been increased overall by a small percentage of the tool’s total lifespan. In this situation, wood tools for example may not get that much extra durability, but diamond tools would get a good while longer to use. Obviously it would be hard to get and expensive in terms of exp to attach. I also considered the idea of lifespan having a II or III stage as well, to increase the percentage increase slightly each time, and maybe even for Lifespan III to have a special bonus effect where it has a chance to keep your tool/armour going for a little while longer after it reaches 0 durability (maybe a chance effect where there is a small chance your tool can mine another block or two after it should break). Also Lifespan should not be able to go with unbreaking AND mending at the same time, for balancing purposes.