i try to keep a maximum of 10 duplicates aside from the set for my collection, though usually more around 5 (the trade demand is never quite so high that any one person will ever ask you for more than 4 of one species). try to keep your extras and main collection distinctly separate. i will take any event, petshop, or very specific regular tubes you dont want, but aside from that i would like to save my space as well. and really, dont rule out deleting some things as well - its better to delete even quasi-rare pets (like old hunts of limited or event betas) than to give loads of them away as free because that decreases their value significantly (we dont want that now do we?).
i kin chat anytime before 4:30 in the coming couple of days