There was an episode where a Starfury was damaged by the Streib and Sheridan was kidnapped. The pilot had to choose between his life support and speed. Since he had already received a lethal dose of radiation from the damage to his ship he chose speed.
(where Lennier is trying to find out how the Centauri are attacking the LoNAW) In this episode Lennier's problems arose from having to shut all his systems down to avoid being detected. Had he been able to keep his power plant running at full he may not have been in such a pickle regarding his oxygen reserve.
However I take your point that even a life support can only recycle so much. That being said I wouldn't want to go anywhere without at least a weeks supply of food, air and water, just in case I got lost or hit an iceberg.
Timstone: PM
unrelated link to terraforming
http://www.Users.globalnet.co.uk/~mfogg/
[ April 19, 2004, 19:33: Message edited by: Nomor ]