2.3 Specification and Product Development section requires that you have a process in place for the development of new products. Essentially, you need to document your R&D process, e.g. the procedure for formulating for new products or changes to existing products from concept to commercialization. You will also need to address how specification criteria are arrived at (to show they are not plucked out of thin air, but based on trials, tests, etc.). Impacts to your food safety plan will need to be reflected when a new product is added or a product is change, like a HACCP reassessment.
Shelf life -- you will need to do shelf life trials to validate your products' storage, shelf life, stability, and consumer handling. If you determine shelf life testing is not necessary (i.e. you have previous data from a similar product), then you will need to document the justification for that decision with supporting evidence.
Like everything in SQF, you must keep records of all of this and show approvals on product design, processes, shelf life trials, etc.