The reason behind thinking the spars will need to be replaced:
After 30 years, every single connection on the rig
is going to be suspect. The spars maybe ALU but the fittings will be SS. The mast head, mast step, and every single rivet/screw will all be sources of galvanic action.
I am speculating the last time the rig
was throughly checked was 12 years ago when the shrouds were replaced.