How About Hearts?

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

NorthEastSouthWest
1 Pass 1 Pass
2 Pass 4 NT Pass
5 Pass 6 All pass

NorthEastSouthWest
1 Pass 1 Pass
2 Pass 3 Pass
3 Pass 4 NT Pass
5 Pass 6 NT All pass

The first South player fell in love with his spades. A six-card suit headed by the A K Q 10 is a Jack shy of a self-supporting suit. To be sure, if we give declarer the J for the 10, that still wouldn't be enough, but it would be at least a little more tolerable to expect that the outstanding spades would fall in 4 rounds than to suppose they would in three.
There really isn't much to say about the hand, it being a bit too obvious to mention why insisting on the spades won't work and choosing no trump allows declarer the luxury of switching to hearts for his necessary tricks when spades don't offer a running suit.
Well, suppose hearts had split unevenly and declarer missed the J. Oh, c'mon. Of course both suits might refuse to behave. No one's saying this is an open sesame to all successful contracts. Hearts could have split badly (give West all four outstanding hearts and declarer couldn't even guess right to pick up the J) and spades might have split benignly (just put the J with the short hand) and that's the point, that in no trump you (often, not always, of course) have the luxury of turning your attention to another suit if the suit you expected to be your flagship turns on you.