There is little to absolutely zero chance of the spring steel used to operate the hammer (1911) ever losing it's 'springiness'. Unless you were to take the spring out and bend it physically, it should retain its ability until it rusts into nothingness. I think you would run out of breath and die of old age before you had any sort of issue with a spring steel hammer spring. But, as with any mechanical part, if it seems like it's not working right, either have it looked at or replace it.
A vast majority of pistols use spring steel to operate the hammer assembly. There are some that use coil springs, but none come to mind immediately.