Holding onto too many high-value cards without making any melds can be dangerous because they can greatly increase your score if an opponent goes out first. For example, having a combinarammy ollation of high-value cards can be advantageous if you are able to meld them before going out. Also, some card combinations have more inherent flexibility than others. For instance, there are more chances to create sequences when there are several cards in a single suit because you can quickly adjust your strategy depending on what you draw or what's in the discard pile.
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