You really can't tell with much accuracy. Growth rates can vary dramatically depending on husbandry. Veileds for example can take anywhere from 4 to 8 months to reach maturity.
Here she is!! (She's in the middle of shedding right now, but there she is. lol) Sorry the picture is so blurry. I had to take it with my ipod b/c my camera is MIA right now. lol
Thanks!! That helps a lot as well!! I had already read somewhere that you needed to have the egg laying bin and all set up, but I didn't know that it happened very often.