The effect of age on drying out wood in cabs is usually positive, as long as it was good wood to begin with. Speakers are usually good for 30 plus years, then age affects the glue, etc. As for guitar wood, yes and no, as the old growth wood usually is better. Just my .02 based on having guitars 60 years old vs newer production guitars. There's a lot of other factors, of course...finish thickness/type, how old the wood is that was used (if it's a replica made of old wood), how dense or dry it is, etc, etc. The combinations are basically endless, IMO.