This totally depends on environmental conditions with temperature as one of the most important. Some geckos can reach maturity with 8 months, when it can take up to almost two years with others (kept under very poor conditions)!
I have a Male that is at leaste 5 years old no make it 6 years because I have had him a year, a year ago he was 65 grams and today he is almost 90 grams. Also that pair never mated before and their 1st clutch hatched April 19th and 22nd.
Males, from my understanding take longer to mature physically. But sexually they are ready before females. I have heard it could take up to a year and a half for them to reach their "full grown" stage. But even then, they can always gain weight.
Reptiles never stop growing... They are not like mamals... A reptile will continue to grow for its entire life span... Major growth occures during the first year or two depending on the species...
Leos, under proper conditions reach adult status @ about 10 months... It is usually a good idea to wait to breed females @ a year old... 40 grams is usually a safe weight to breed females depending on overall body condition...