Final model: 'batch*time' | 'batch + time' | 'time'.
Overall shelf life (minimum over batches).
Model selection steps: term tested, p-value, decision.
Shelf life per batch (NaN when the bound never crosses within maxTime).
Fitted mean and confidence bounds for a batch at a time.
Optional
Final model: 'batch*time' | 'batch + time' | 'time'.