Is not a must but a beneficial duration of investment to some persons because your invested money determines how long is going to be, for example you and I have a plan of getting $26k worth of Bitcoin and you started with the weekly investment of $100 and in five years you should be having nothing less than $26k in Bitcoin meanwhile instead of using the same amount you are using I choose $50 based on financial insolvent, so actually in the five years I will be having only $13,044 in Bitcoin while you have meet your target in just five years I'm still half way to it, so to get this I will have to give myself another five years to get there making it 10 years I have spent to achieve it, so actually this example is just a little explanation to show you that 10 year investment is not a must but with your plan it can take up to the years I have explained.