I would never convert all my 'spare' money in btc, I'd rather have a few different type of currencies in case something would ever go wrong.
But it would also depend on the amount you are saving up in btc. if you have a million dollars spare, I wouldn't put 50% of it in bitcoin to be honest, but if it was a smaller amount I would.
It is better to be safe in cryptocurrencies rather than going all in on investments because it is very risky for the people around there who are greedy especially if they don't have any knowledge about the investments because it will often lead for a loss rather than earnings. It is better for them to just spend a small percentage of their money for investment to be sure that they will not get a huge loss.