What a glorious way to eat your veggies!
Place completely cooled muffins into gallon sized freezer zip bags in one layer, about 9 will fit in a bag. Using a straw, remove any excess air and zip the bag. Place in the freezer, it's ok to stack the bags on top of each other, for up to 2 months (good luck getting them to last that long!). Remove as many muffins as you need at a time and either thaw at room temperature or heat in the toaster oven or microwave. Frost with the sweetened cream cheese, if desired.
The difference between regular milled flax and cold milled is the process. Cold milled gently grinds the seeds without significantly raising the temperature, which preserves nutrients and extends the shelf life to 22 months. For a substitute, you can add additional flour, but flax really provides excellent nutritional benefits. 2 tablespoons = 2800 mg omega3, 3 g protein, and 4 g fiber.