Titan Resurfacing through Biothermal Energy?

Linked above is a paper brought to my attention yesterday. In this paper by Dirk Schulze-Makuch and David H. Grinspoon, the authors suggest that heating produced by organisms near Titan's surface could explain the relatively youthful surface of Titan. Their contention is that organisms could have evolved in hot springs and in temporary crater H2O lakes, and later may have evolved to survive on Titan's surface, metabolizing photochemically produced acetylene. The heat from chemical reactions produced by the organisms, the authors posit, could then be enough to produce the energy needed for the cryovolcanism observed by RADAR.

Personally, I feel there are a number of problems with the arguments in this paper. First, the environments suggested for the development of life are fairly limited in extent but yet the authors require life to be fairly widespread for their heating mechanism to work. They get around this by suggesting the life could have evolved to survive the surrounding terrain, but I would think that much of the energy it produced would go toward not just running the reactions that keep it going, but to also keep the water in its body from freezing. I can buy the alternative metabolic pathways argument just based on the diversity seen on Earth, but the requirement to keep its body from freezing, let alone have enough excess heat to power volcanoes, seems to be a brick wall for life to overcome.