I've heard that keeping batteries in the refrigerator ensures long battery shelf-life. Is this true? If not, where did this information come from?
It depends on the batteries.
For alkaline batteries, no.
According to Kodak,
Ideally cells should be stored in a cool, dry place away from direct sunlight, radiators, and other heat sources. Refrigeration is not necessary, nor is it recommended. If you do store batteries in the refrigerator, let them warm up to room temperature (takes about two hours) and wipe off all condensation before use. Freezing is not recommended.
Do not refrigerate Duracell batteries, this will not make them last longer.
No, storage in a refrigerator or freezer is not required or recommended for batteries produced today. Cold temperature storage can in fact harm batteries if condensation results in corroded contacts or label or seal damage due to extreme temperature storage. To maximize performance and shelf life, store batteries at normal room temperatures (68°F to 78°F or 20°C to 25°C) with moderated humidity levels (35 to 65% RH).
According to M/A-COM, who apparently make batteries rechargeable batteries for radios,
Keep battery packs in a cool, dry storage area (32 to 86°F (0 to 30°C)). Refrigeration is recommended, but freezers should be avoided. When refrigerated, the battery pack should be placed in a plastic bag to protect against condensation.
Storing Li-ion batteries at low temperatures does appear to reduce the rate of capacity loss (page 4, figure 5). They only compared two storage temperatures (5C and 35C), but the batteries stored in the former displayed substantially less loss in capacity.