Maturation size of D. auratus

In October, I purchased some sub-adult auratus (Costa Rican morph) at a herp show. However, it was busy when I finally picked the animals up before leaving, and I was unable to ask how old the darts were. They were slightly bigger than other auratus at the show, so by my rough estimate, I'm guessing they were four months old at the time, provided it takes 3 months to morph and another month to put on the added size.

It's a bit over two months later, and the largest frog is about 2.5 cm from "tail" to snout. While I greatly enjoy dart frogs and would like to get deeper into the hobby, they're not yet my area of expertise and I'd appreciate it if you guys could give me a better estimate of how old they might be, how old most auratus are when sold at herp shows (they had adult coloration) or how old/large your frogs have been at first maturation. One of the things I most look forward to is when they start calling and laying eggs, and since auratus apparently call very softly, I'd like to know when to start listening.

My apartment is also rather dry, and while my best estimate of when to expect eggs is in May when I'd be at home, if they start before then I'd need to check for eggs every day since the current water features installed dry out every so often.

While I'll take all precautions some time before they approach adult size, it's really driving me nuts to have such a bad estimate of their age, given my inexperience with the species.

In any event, thanks in advance for any advice.

Peter