Is the length and intensity of feelings and emotions limited?
The key terms to help understand the answers about the duration and intensity of experiences over time would likely include habituation, emotion, and pain. You might be surprised by how scientists use these terms differently than most people. Consider an intro psych textbook or wikipedia.

For example, emotions are generally defined as being brief, transitory affective states. If someone has a negative feeling that lasts for hours, psychologists might call that a mood. If a person has a negative feeling that lasts for years, psychologists generally use other labels such as personality. The experience in a moment might be the same between these cases.

There are some assumptions in your question that are not shared by most research or clinical psychologists or neuroscientists. For example, emotions aren't deterministically caused by hormones.