I think the 5 gallons at a time practice is a good one, but I wouldn't let the bio sit around for more than a couple of weeks, w/o environmental conditioning. The fuel is hydrophilic, meaning it likes water. It's also a good solvent, meaning that it will take on debris liberated from the composition of the container, suspend said debris and I think it has the the potential to increase fuel filter fouling.
I received this information from a biodiesel dispenser builder/maint crew. As they were maintaining a commerical facility, flushing the lines, changing the charcoal filter and dessication/moisture collector and the 1 micron filter hidden in the housing of the pump.
A lot of science goes into the care of a supply of biodiesel.
... just my 2 cents...
When I asked about a good way to store it for use on the road, they just said a standard kerosene jerry can would be fine, but after a week or so, it'd be better to consume it all quickly to avoid the environmental contamination.
-Jon