Although I have been enjoying my enemas for many, many years I am in the minor leagues when it comes to quantity. Two quarts is my comfortable volume for cleansing or rinsing, with about three quarts the most I have ever given myself. That said, how long I retain it depends on the purpose and type of enema.
If my goal is a deep clean, whether plain, soapy, or salt, I rarely hold it for more than a few minutes. I do not have an inflatable nozzle, so I depend solely on pucker power.
When indulging in my favorite coffee enema of one quart, my goal is twenty to thirty minutes retention, but if I get distracted when the urge to expel comes I can hold almost indefinitely. While retaining my coffee I usually check for activity here on Zity, or masturbate, or both, and often the time just slips away. It is common for me to go to one hour and the longest I have retained coffee is about two hours. At that time, to get the rest of it out requires another enema or glycerin or something to kick start my colon.
A few times, when bored during the day, I give myself one or two quick squeezes with the bulb and hold it until it is gone, which is hours later.