After forty years or so I suspect any guitar is going to be liable to belly up a bit. And forty years is only middle-aged for a decent guitar. Guitars are multi-generational creatures, like giant tortoises or grey parrots.

But, even aside from that side of it, the tension rod/sound post, does affect the way the vibrations are transmitted from the bridge to the guitar, for the good I'd say.

I'd say it's worth trying, even in a new guitar. Nothing to lose really, since it's the easiest thing in the world to loosen, or even remove entirely, the tension rod, and to put it back or tighten it when desired..

I'm not sure whether I'm ging to tell all the guitar players I know about it, or keep shtum and let them be impressed by how my guitar is sounding these days...