depending on size but id say 2 years time in September to October for December lay and Febuaury hatch. But remember you need to cool them for a few months then powerfeed for a few weeks after cooling then introduce your pairs. Make sure she is in top condition not fat also with him make sure hes in good nick as he will also determine how many eggs are fertilised, slugs are often down to the maleAlways add male to females cage not the other way round. cheers and good luck james