Do Aluminum masts have a "working life"?

[Cheechako]

I doubt an aluminum spar will ever reach it's cycle fatigue limit... they just aren't cycled far enough to be a problem. The problems , as noted above, are corrosion and also stress risers... any opening cut in the mast, especially near stress points are subject to cracking over time... no problem ....in most cases just weld it and/or put a structural plate riveted over.

[Mainebristol]

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.

[Cheechako]

Yes and an airplane wing might cyles +/- a few feet.... hundreds of thousands or even millions of times... a mast much less....