It is good to have a target but that target must be based on sound reasoning. If you have just pulled a number out of thin air then you might as well not have a target at all.
15kg a year sounds like a good target, but what is it based on? Why 15kg and not 16, or 14? 15 sounds good and we all like a round number. If we think that silver is massively underpriced and will soon be $100 an ounce then we don't need to stack that much to make a lot of fiat. If we think that there will be a global collapse of the dollar or that the banks are going to give the depositors a haircut then we might want to stack a whole lot higher.
I couldn't tell you my target, I couldn't even estimate how much I have in Gold silver or platinum stacked up around the place with the numis and the coins and the rounds and the bars and the unallocated and the stuff I have sitting on Maggie's shelf waiting for me to pull my finger out and pay for.
For me, stacking silver is a way of quarantining some of my disposable income from things like the shopping, car servicing, an extra round of drinks on holiday etc. All the little things that can add up.
It is the most boring thing on earth but I have started writing down each and every expenditure each day, money spent on petrol, parking meters, coffees etc. At the end of the week when I ask myself where has all my money gone... I just check the book. And I wonder if maybe having breakfast down the market with a couple of coffees is better than having an ounce of silver, I enjoyed it at the time but now it is gone.