When the config option "regenerate_read_only_objects" is set to "no" flexible models are not modified on open. We saw significant improvement in performance when we had the option set to "no", but since we have flexible models, we need to set it to "yes" instead. I would like to see an option added, maybe called "changed" or some other value, that would ONLY regenerate models that have a variation applied to them within the context (assembly level features, flexible model, …). If a model has no changes at that level, I would want the model to not be regenerated.
