I am not entirely sure as I am from another corner of the world, but a quick (non-conclusive) websearch, for example here and here, suggests something between 25 and 60 years. Assuming that you want thick trees (= significantly more value), I'd aim for the upper end of this range. Besides, teak is supposed to grow slowly for best quality.
Remember that the currently oh so modern term "sustainability" was coined 300 years ago by Hans Carl v. Carlowitz in Germany with regards to forestry. I'm from the Black Forest myself, where wood was (and to some degree still is) a significant source of income for centuries. If you intend to plant trees for your own retirement, I hope that you are a) quite young and b) have a "Plan B". Here in the Black Forest one sells trees that were planted by the grandfather or father and plants trees for the benefit of children and grandchildren.
If you simply happen to own a piece of land and have no better use for it, go for it and plant a few trees, but do it for fun, not for economic reasons. If you can sell a bit of timber in a few decades, it will be a neat little windfall, but don't count on it, there simply are too many things that may go wrong.