The most important thing to remember about PD is that the actual cleaning of the blood and fluid removal happens between exchanges. Not during the exchanges themselves. So, the key is the amount of time the PD fluid is inside your body. Be aware however, that in PD, it is not necessarily the greater the amount of time the fluid stays inside your peritoneal cavity, the better the dialysis you get.
The rate of toxin and fluid removal increases to start with but gradually tapers off and left for too long, there is actually a possibility of the revers happening - the toxins and water might actually go back from the fluid into your blood. So, the key is to figure out what the optimal time to keep the fluid inside is. this can be done by doing the Peritoneal Equilibrium Test. The test typically gives a result that can be one among the following: Low, Low-average, High-average and High. This basically indicates what kind of a transporter you are. These words refer to the rate of transfer of toxins and water across your peritoneal membrane.
Generally people with either low or low-average PET results will do well to keep the PD fluid inside them for longer periods of time than people with high or high-average PET results. If you are low or low-average, it might be a good idea to consider using a PD cycler which will dialyse you at night.