There are companies that do accelerated shelf life testing (just Google; you'll find many), but real time testing is preferred, at least with respect to validation. With acidified foods such as pickles obviously pH vs. time would most likely be your number one concern. Under the FDA and or USDA websites you can see how acidic a product must be to be considered safe ambient temperatures. Water activity also plays a role in safe ambient shelflife.
Keep in mind that if your products make someone ill due to pathogen contamination prior to the label stated shelf life and you haven't really done your homework well the FDA is ready to pounce. That would be a "Use By" date. If, however the product(s) go bad and it's just a quality issue (foul taste, discoloration, etc.) it's a different story ("Best By" date).
The following is from this site:
You may also find this doc from FDA useful:
Real Time vs. Accelerated Shelf Life Studies
There are two basic methods for performing shelf life studies: Real Time and Accelerated. Real time studies store the product under the normal conditions of the product for a period of time greater than the expected shelf life. The product is checked at regular intervals to determine the point of product deterioration.
Accelerated shelf life studies attempt to predict the shelf life of a product without running a full length storage trial. This type of study is usually used for product with a longer shelf life. Acceleration factors such as temperature are applied to the product to attempt to increase the rate of deterioration. The data can be used in predictive mathematical models to project spoilage rates and bacterial growth. Accelerated studies should be used with caution, you must know a good deal about your specific product formulation and properties to interpret the data optimally.
It is always recommended that when an Accelerated study is selected that a dual, real-time study is also run concurrently to validate the projected data.
7 Steps to Determine Shelf Life
1. Identify what may cause the food to spoil ◦Product: raw materials, formulation, water activity, pH, oxygen availability, preservatives
◦Process: Processing activities, packaging, storage conditions
2. Decide which tests to use
◦Sensory: odor, appearance, flavor texture
◦Microbiological: spoilage and pathogenic organisms
◦Chemical: pH, free fatty acids, headspace analysis, etc.
◦Physical: product abuse storage and handling
3. Plan the shelf-life requirements
◦What tests need to be done
◦How long will the studies be run
◦How many samples for each test
◦How many samples for the entire study
◦What are the storage conditions
◦When will the study be run
4. Run the Shelf Life study
◦At time intervals established in step 3.
◦Run the appropriate tests in step 2
5. Determine the shelf life
◦Eventually a point is reached when the product no longer meets requirements for quality or safety, which is the shelf life
◦Usually a pre determined point is established to end the study if quality and safety are not affected
6. Establish working shelf life
◦Working shelf life will be less than actual shelf life due to real world factors such as storage conditions and potential product abuse
7. Once product is released to the market -> Monitor Shelf Life
◦Investigate any customer complaints or failures
◦Evaluate samples from production and distribution to validate study results