As a general rule, launder your bath towel (or swap in a clean one) at least once a week and your washcloth a couple times a week. Wash towels more frequently if you're sick to avoid reinfection.
It is inherently less precise than a level teaspoon. 1 heaping tsp means you pretty much try to get as big a pile of sugar onto the spoon as you can, without spilling it. It's a little over a smidgen more than a rounded teaspoon. Helpful hint: Don't try to measure a heaping teaspoon when dealing with liquids.
They're roughly 2–3 tablespoons.