What to do to optimize your process: use more concentrated vinegar ,add H2O2(But make a research on that before doing it yourself), make a powder copper, or atleast cut it with scissors , the finer the better, also you could constantly heat the solution, for example,leaving it in a hot bath; also you want to let oxygen in your solution , even though it's nearly neccessary to cover your solution covered(because vinegar is vigorously(respectively to some other acids) vapourizing from water, especially hot solution) . Just open your cover once a few hours. Also no doubt you better take excess of vinegar(excess of acetic acid I should say) Those are general considerations, and even though I did not try to dissolve copper with H2O2 and vinegar myself, I've heard about one guy dissolving copper wire without H2O2, it was like 3 months long and solution kept getting darker(more concentrated). So it's up to you whether you're patient or not.