Lots of species of salak (nearly 2 dozen?), and a huge amount of variation within species (taste, texture, pollination, etc). But 3-4 years would be a good guess in good conditions.
Try to cultivate all 7 to maturity, and plant a bit denser than you'd prefer in the end. Only the Bali variants of S. zalacca are monoecious. Otherwise you'll need at least one male (you can remove excess males at that point; if you need to remove more plants, you can thin females by productivity or quality)
Beware the thorns; these plants have an impressive armament
Oh, and you've probably noticed that they sprout in a rather odd manner, pushing a plug out of one end, which then branches off. I'll warn you that they also grow in a rather odd manner aboveground too; new leaves look like dead sticks. Don't worry, they'll open up eventually. You get used to it, but the first time I was really concerned that I had killed my plants when all I had in the pot was a "stick" sticking out of the soil.