We volunteer at Corps of Engineers parks and state parks and don't have a problem working 15 to 20 hours for each of us but we usually negotiate for a total of 24 hours for the site. We will not work for a commercial park of any kind because a commercial enterprise will always have a "bottom line" mentality and we did that for a lifetime already. We never have had a problem finding volunteer positions. We simply look on a map for a new place that looks interesting and start making phone calls to parks and ask the question..."we are experienced volunteers and would enjoy experiencing your park for 3 or 4 months. May I speak to your volunteer coordinator?" Never a problem finding a "work".