Most important are the parts that you happen to have around. The more watts the more energy you will consume over time. Half watt seems to work fine. Less might also work. More than 10 watts seems like a waste of power.
My electrical engineer brother solved this problem for me a couple of years ago. With a quick calculation using ohm's law, he handed me a resistor and said to hook it up to a 12volt power source (from some scrapped household appliance) to give about a half watt of heat. I wrapped the resistor...
I highly recommend Roscoes on the east side for an eclectic collection of local brews, great ambience and probably the best bar food I that I've had. Also second the idea for a day trip to Pfriem in Hood River especially for their outstanding lagers.
I have a related question. Does CO2 pressure inhibit the aging process of aged beers (e.g., RIS and barleywine)? Is it OK to age in a keg at full carbonation? Should you reduce the carbonation during aging? Should aging be done in a secondary fermenter with no pressure?
I have Beersmith V2. "Hops age tool" is under the "tools" pull-down menu at the top and in the tools menu at the side. Tried it. Works great in that it's easy to use. Thanks day trppr!
Highly recommend Rosco's in east Portland for great collection of local brews and great food with fun atmosphere. You can check their continuously changing offerings at their live cam chalkboard at http://www.roscoespdx.com.