In Mary Roach's Packing for Mars, she writes about NASA doing research and performing tests on how long someone can go without a shower. The test subjects described the first couple days without showering to be the most uncomfortable, but after getting past the initial discomfort, they were able to adjust and didn't feel strong inclinations to shower anymore. When our body is replenishing the natural oils on recently cleaned skin, that's when we feel most icky, but once it achieves a balanced state, we feel less gross if that makes sense.