I think there are a couple of people that could hold BTC for more than 3 years because the people I know who are into Bitcoins hold their btc's even more than 5 years and are still holding on to them up until now. So the answer would be a lot! Imagine how many people now are holding bitcoins, hopefully it will be enough for circulation too.
Yes, many people are holding bitcoins from a very long time with themselves. They are just waiting for their opportune moment, which havent arrived yet. I think they are doing right because patience is the most important step to work with.
I know it is hard but success without patience is not possible, you must have to be patient and thats exactly what the people are doing by holding their bitcoins.
There are so many people actually holding it, but sometimes they need money so they will spend their bitcoins this is normal because we live in this world where money is the boss over nearly everything.
I hold it long now i will continue to hold it because i know that bitcoin will rise very high in the future.