Hell yeah, to get what all men want...MORE. I dont use durantium lately, as I've been on a beam kick, but if you love the durantium mass driver, which can be OP in numbers, then you need A LOT of Durantium. Or lets say there is only 1 Elurium in your ZOC - and that elurium is used on a support ship to enhance beams for your fleet. well, you can get 2, 3, 4, or even 5 resources from 1, with appropriate upgrades. Now you can have 5 fleets, each with a single support ship, or have 5 planets be practically immune to invasion with the elurium defense shield.
Its only worth getting more, if you value the resource highly.