The O-ring store has technical information on their site, such as chemical resistance, temperature ratings, and shelf life. In their section on elastomers, it seems like Silicone would be a good choice. In another section it indicates that silicone has an unlimited shelf life.
It also indicates that some selections take 4-6 weeks to fulfill. If you're stocking up, this wouldn't be an issue.
Silicone O-Rings FDA (VMQ)
Silicone O-Rings / VMQ: In the Silicone family, you will find compounds which are superior as static seals in extreme temperature conditions. Standard compounds handle operating temperatures -85º to +400ºF. Silicone compounds are popular in food and medical applications because they are very clean and do not impart odor or taste. Special Phenyl silicones can be used down to -148°F.
Operating temperature: -75° to +400F°