Lets say you were shopping for a 40' trawler, late 1970s or early 1980s, and you found one you liked. If it had teak decks that appeared to be in good condition, would the teak decks be a deal-breaker for you? Does your current boat have teak decks?
No I would not buy a older boat with teak decks.
In my opinion there is simple too much risk.
Couple hundreds of fasteners, a balsa core and 30 or more years and you have a recipe for a huge repair bill down the road.
When we were looking for our next boat we wrote up a list of wants, needs, deal breakers. Teak decking over a balsa core was high on the list of deal breakers.
Please understand, I'm not saying all teak decks are bad. I'm not saying that all teak decks over balsa are bad. What I am saying, is to us, as prospective boat buyers, teak decks over balsa represented too much risk.
For us...
Fiberglass over balsa was acceptable
Teak over synthetic coring was acceptable
Fiberglass over synthetic coring was preferred.
That's one of the reasons we bought our Bayliner 4788
No balsa anywhere. All coring is synthetic.