We either buy when the market is down or we buy in bulk. The reason is that when the market is red, the purchasing power of the money we have is more and we can buy more goods and servises that we could before. Secondly, even if the market is not down, if you purchase in bulk, your average cost is redused as a result of which you spend less than you would have spent if the amount of the goods bought were not huge.
Large purchases are never a good idea, regardless of the market we're in, and especially not if the market hasn't been tanked to the bottom. You are either a bit confused with how you want to explain yourself, or just completely miss the target. Either way, buying and selling should always be done in smaller fractions -- bulk purchases, as you like to call them, make you too dependent on one particular outcome, which is never a good thing in this market. I like to work with 5-10% buy or sale fractions per time, which gives me enough freedom to catch up on a decline, or unload more coins in case the market keeps going up, all to maximize my profits. In this case it's largely a matter of logical thinking....