I have been buying bitcoin when the price was around 400$-450$.Most of my bitcoins are bought at that price around 40 BTC and remaining at less then 600$ price.i have been holding btc in paper wallet since then and already my stash in usd is 6 times.
here is one of my tx

what i want to know is please suggest some ways to invest my bitcoin at zero risk to earn some profit.Even 0.8% to 1% profit per month is good for me but it should be risk free.i don't mind the profit percentage but risk should not be there.if you have some suggestions please post that too,if i should keep holding for more years and if yes how long should i hold?
Theres no risk free on this world when you are pertaining on making investment and lucky for you that you did able to buy cheap coins wayback before which do already give you enourmous profits as of now on the current rate.If i were you if you dont like to risk on investment since that 0% risk doesnt really exist at all and even holding your bitcoin on paper wallet do still have some risk on losing it.