Each site will have a unique set of circumstances for the resident volunteer program. Most sites require a minimum of 40 hours per week for a couple and 32 hours a week for a single person living on an RV pad. But, some sites may require more or fewer hours. It's important to make sure both the volunteers and the host agency are very clear on the hour-requirements BEFORE the volunteers commit to the site.
Guidelines suggest that the number of hours required and the value of the type of work assigned should roughly equal the "going rate" for a camper pad in the local area. For this reason, the requirements will vary widely from place to place.
But, volunteers are encouraged to give more time and energy than the "minimum required". The more of yourself you invest, the more fulfilling will be your experience. On national wildlife refuges, it is rare (maybe even non-existent!) for any monetary compensation to be given for extra hours.
At some locations, the minimum hours might be assigned to a specific job at a specific time; however, there may be additional experiences you will be offered an opportunity to benefit from if you're willing to do so "above and beyond" the minimum requirements. This type of scheduling is necessary in order to keep the basic operations and needs of the refuge covered. For example, if sea turtles are hatching, you may have the opportunity to participate in "Turtle Watch" in the evenings, but those hours will not likely be substituted for your assigned duties.