Food crisps/browns/undergoes something called a Maillard reaction at 250 f (120 C). This bit of kitchen chemistry is named after Louis Maillard, a French chemist, who in 1910, discovered a reaction between amino acids and sugar during the cooking process. The Maillard reaction is noteworthy for two reasons:
1) It is different than carmelization (the browning of sugar) which happens 365 f (180C). Foods with a low sugar content such as coffee, cocoa, meats all brown through the Maillard reaction.
2)The Maillard reaction creates 100s of new compounds; this along with the presence of amino acids develops a taste that is regarded as more complex and flavorful than caramelized sugars. For this reason, commercially manufactured foods, things colas, syrups and industrial soup/gravy aren't just sweetened, they are flavored by introducing alkalis, acids and salts to sweeteners to produce bolder flavors.
I mention all of this not so much to geek out on the science, but to help identify the waffle issue at hand. The temperature you need to crisp a floury food like a waffle is actually quite low, so you don't have to crank the temp up - the caveat here is if your first waffle was just right and your next few were lacking in the desired crispness, you might have wait for the waffle maker to warm up between waffles.
So if it isn't the heat, it must be the humidity, or at least the amount of liquid in your recipe needs to be adjusted - for moisture is the sworn enemy of crispness. And if you're wondering how can a recipe have too much liquid if you followed it exactly, well not all recipes are created equal - and if your retort to that is - I've used this one before or the author is trustworthy, well, sometimes the ingredients can be the cause of problems.
The issue could rest with the flour. There is a bit of kitchen Apocrypha that claims ambient humidity effects the level of moisture in flour. Maybe. Maybe if you stored flour in an open container in a 100% humidity environment - a sauna/a Pacific atoll/New Orleans - then maybe the flour would absorb as little as teaspoon of water per pound of flour from the air - maybe, not likely though. More likely is the type of flour being used. Cake & pastry flour need very little water, while a high protein flour, like bread flour, is very thirsty and will really drink up any liquid you put into it. Adding extra water or milk to make the consistency look right is ultimately dooming your potential crispness.
But it probably isn't the flour and since milk is milk, that really isn't the source of your woes either. An improvising cook might feel compelled to add a little more sugar to help brown things up. But this would be the wrong thing to do. Not only because crispness and caramelization casual in their association - it is because sugar is considered a liquid in cooking since it converts to a liquid as it heats. Unless you are going sugar crazy, the problem likely isn't sugar. The uncrisp waffles could be a result of butter; low grade butter contains more moisture than expensive high fat butters, but I'd bet the culprit here is eggy in nature.
Most recipes are designed to use large eggs - an egg that weighs about 2 ozs, sans shell. But not all eggs are equal in their largeness: The 2 oz. average is not for an individual egg, rather it is meted out over a dozen eggs. So with any given egg there could be extra liquid going into the waffle batter. And if you used an extra-large egg there could be as much as an extra 1/2oz. of liquid per egg going into a recipe.
In order to avoid spongy, uncrisp waffles, I'm going to throw you a couple ideas: Reduce liquid by a 1/4 cup. Make a waffle see how you like the taste and consistency - too dry or tough add a little more liquid. For extra, crisp insurance: Coat your waffle iron with a healthy layer of oil before puring in the batter. Oil transfers heat quickly and more evenly than liquids like a waffle batter. Oiling your appliance is like installing a little layer of insulation on the cooking surface.
So moderate heat, give the waffle maker time to heat up between waffles, reduce the liquids in the recipe and coat the waffle iron with a thin layer of oil. Each of things should make your waffles so crisp, the syrup will pool in the pockets rather than soak on in.