A) bitcoin is a bubble, sell to the strength. I would suggest selling with a predetermined schedule, such as 1% of the remaining holdings per month, or 10-25% every time it doubles.
+1
I wrote simple Excell, based on your great idea. "You have an AMOUNT of btc. When price DOUBLE, SELL 25%"
In Excell, you can configure (4 parameters) and can see your wealth based on USD/BTC price
1. btc AMOUNT you wish to spend.
2. parameter "when price (DOUBLE=200%)" you can configure e.g. 5%, 10% 100% ... 1000% as you wish
3. (SELL=%25) change this setting (1%, 2%, 5%, 10%, ... %20, %30)
4. starting selling price e.g. $160
Again GREAT IDEA. Now it is EASY, how much and when to sell. As easy as bot can do it. I'll add few REINVEST parameter "When price HALVES invest 10% from your profit" :-) Perpetuum mobile