Missed Opportunities

Q
K 10 6 5
Q J 10 2
K 9 8 2
10 6 4 3 2 J 9 5
A 9 4 Q J 7 3
K 7 9 8 4 3
10 7 4 Q 5
A K 8 7
8 2
A 6 5
A J 6 3

Three no. Declarer was sitting pretty with the opening lead of the 10 of clubs, no less, East contributing to the generosity and removing all doubt by playing the queen. So declarer has 4 club winners, three diamond and 3 spade, with no possibility that the defense can run more than two hearts unless he gives them the power.
Declarer went to the queen of spades, took a losing diamond finesse and ducked the 4 of hearts lead to East. Here the two sides traded lost opportunities (which isn't to say they were obvious and foolishly missed). Had declarer hopped up with the king, he would have gotten an 11th winner in top cards, and when he ducked, the defense would have had its third trick had East returned a heart to his partner's ace. Declarer wisely ducked the heart lead, of course, because by so doing, he cannot suffer more than two quick heart winners by the defense, which he can live with. By going up, declarer could lose three heart tricks, and in fact, there's a layout by which he could lose four and be set! Which probably wouldn't be pleasing to his partner. As for the defense, they were to have another chance at a third trick, but would blow that one too for a near bottom score.
Back came a spade from East, won with the ace, and now declarer went to dummy after cashing the ace of diamonds, to finish off the suit, sluffing a heart from the closed hand, then cashing dummy's clubs to come back to the closed hand with the last club, East sluffing the jack of spades. West sluffed useless clubs on the diamonds, a good procedure, for though he's now got to make a tough decision on club leads, it's wise to put this decision off as long as one can. The hand might be clarified a few tricks later, and then again, it might not be.
The crunch came at the cashing of the last club. The closed hand had K 8 in spades left. West, with the ace of hearts and 10 6 in spades had to make a decision... and decided to keep his ace of hearts allowing declarer a winner with his last spade.
Could West have known? I'm gonna say yes with the jettison of the jack by his partner. Unless East was trying to play cute, and there's no reason to do so, for he'd mislead his partner more than declarer, that jack of spades is his last spade. For why would he throw the jack when he could throw the 8? And if that's his last spade, declarer started with four spades and two hearts and so has 2 spades and no hearts at this point.