My discipline says to trim when any position grows to be too large a fraction of my stock holdings. Also, needed to raise cash to take advantage of what's going on with BBEP trading down in sympathy with LINE. Sold 11% of my holdings today at $17.16. This no doubt has cleared the way for management to announce a huge dividend raise and have this hit the twenties next month. You're welcome ;-)
The difficulty I have selling large amounts of FLY (unlike other lessors) is the impact of my sell orders on the small float of shares. In the past I have therefore limited my selling to days of strong upswings, figuring that the buyer is an idiot computer program, but have sometimes seen the price continue to climb higher.
Not a terrible problem, though, since the sector is hotter than its been in quite a while. I'm guessing that all of the lessors will continue to outperform the market until either the market as a whole tanks or we see negative news for either the sector or the individual companies.
Strum, you and I and every investor has experienced the "Sold one day too soon".
If the guys on the TSLA message board keep pumping that stock, I've threatened to buy 1 share and watch the stock price collapse and never again go higher.