Beyond that, another good lactose tip is that while sheep and goat's milk cheeses may not have "less" lactose, but the individual lactose globules (for lack of a better term here) are inherently smaller than in cow's milk, so many people who find cow's milk intolerable are able to process sheep or goat's milk with little to no problems, and thus can also enjoy most goat and sheep's cheeses without the issues that come along with cow's milk cheeses.

Sheep and goat's milk do in fact have less lactose (sugar) on average than cow's milk. It has nothing to do with the size of "lactose globules," it is because the overall lactose content is typically lower and because many cheeses made with sheep and goat's milk are regularly aged longer and use less whey in the cheese-making process due to the difference in flavor between the milks.

The more important determining factor is how much whey, which contains most of the sugars, is left with the curds in a given cheese-making process and style of cheese.

The reason aged cheese has less lactose is the same reason it is typically desirable (and the same reason beer "wort" has more sugar content than the final beer itself): over time the (lactose) sugar is broken down by bacteria and the byproduct of that process creates additional complex flavors, like lactic acid.

Same idea in beer brewing, except typically this is done with yeast instead of bacteria, though not always. "Sour" beer styles usually get their flavor from the introduction of lactobacillus bacteria.