Over time, a user's perception of a frequently used tool or application will decline if the application itself remains static. Kujala et al. found that with prolonged usage of an application, the impact of "perceived usefulness" of the application declined as a predictor of the attractiveness of software. Non-instrumental factors, in turn, including attractiveness and enjoyment, become increasingly important to engaging user loyalty.
This suggests the importance of continued investment in fostering "delight" (after the Kano model), as well as the value of longitudinal studies of user satisfaction.
Kujala, Sari, Virpi Roto, Kaisa Väänänen-Vainio-Mattila, Evangelos Karapanos, and Arto Sinnelä. “UX Curve: A Method for Evaluating Long-Term User Experience.” Interacting with Computers 23, no. 5 (September 1, 2011): 473–83. https://doi.org/10.1016/j.intcom.2011.06.005.