Well, this is an interesting question. Aluminum
always fatigues, as somebody pointed out, but I work in the flying field and there are plenty of DC3's built in the '30's and '40's still flying around, some with more than fifty thousand hours on them. And yes, their wing spars are original. I'm okay with my Bristol 32's original mast
, over spec'ed by anybody's standard, and extruded back in 1976.
If people trust their lives to an eighty year old wing, I'll trust my boat to a thirty seven year old mast.