Thank for the compliment and I'm happy to help your bankroll last longer. When I gamble for fun I keep playing until it isn't fun any longer. Usually the fun ends when I have lost too much or have played too long. With the ups and downs of blackjack it takes hundreds of hours before regression toward the mean will cause actual results to look like expected results. Furthermore, the player who puts a conservative cap on their winnings is never going to experience the fun of a long hot winning streak. Keep in mind this is just what works for me. You should do what you are comfortable with. Everything I have to say about money management can be summarized by the following two rules (1) don't gamble with money you can't afford to lose, and (2) don't gamble if it isn't fun.
Regarding your second question, there is something to be said about the composition of a hand. The fewer the decks the more this is true. My blackjack appendix 3A and appendix 3B show the exceptions to single- and double-deck blackjack, based on the composition of the hand. These appendices show that the more cards that are in your hand the more inclined you should be to stand. Regarding your 15 against a 10 example, there are two situations in single deck blackjack where you should stand when the 15 is composed of 5 cards, A+A+A+6+6 and A+A+3+5+5. Note that in both of these situations either two fives or two sixes have left the deck which are the two most helpful cards for the player. The two situations where you should be the most inclined to stand if you have a multiple card hand are 16 against a 10 and a 12 against a 3.