Sell everything never. Sell enough to have extra fiat currency for extra expenses like bills.
If 1 BTC goes to 40k selling 30%.
After the massive of bitcoins price, I'm not expecting anymore with the price increase. Because it will happen suddenly and that $40k will be a good price to sell but I don't want to make myself upset again. I want to see the price first to reach at $3k and that will be my mark to sell.
I dont plan to sell my bitcoins until they are worth 100k. I know it is a far fetched dream but I believe that once bitcoin adoption reaches global scale, it will lead to a financial revolution and reset. It will change the way people think about money. At that point, everything might be denominated in BTC instead of FIAT. I bought into btc because I believed in its concept, not because I think the price will go up.
If you will continue to hold your bitcoins for the next few years and keep increasing their amounts every month or year so you can have more chance to have a great growth in your bitcoin portfolio. The price of bitcoin could possible reach $100,000 after at least 10 years from now because of the decrease of the supply and the difficulty to get bitcoin and also at the same time the global adoption.