I'd like to mention that if you tweak this system by selling bitcoins gradually the cash you'll get will be lower than if you sell only when the price doubles. When you divide your 10% of BTC to 10 equal parts and sell 1st part  at 1100, 2nd at 1200 and the last part at 2000 it means that you sell your 10% of BTC for average price of 1550 instead of 2000 which is 77.5% of the price you could get if you didn't split.
Splitting to 2 parts means that you sell half of your 10% holdings at 1500 and another half at 2000. Average price you get is 1750 which is 87.5% of the price if you don't split.
The last extreme example is when you divide your 10% to 100 parts and sell them at 1010, 1020, 1030.. 2000. Average price you get is 1505 which is around 75% of the price if you don't split.
I think splitting makes sense only if you don't believe that the price will actually double at all, or when you already have plenty of bitcoins and every cashout you make gives you some real money and peace of mind.
If the cashouts are small and you don't risk much money holding bitcoins it's better to wait for the price to double or even miss a few cashouts to build your BTC value quicker.