Cam, if by "fridge life" re frozen mayonnaise you're referring to a health risk, that isn't the problem. The ingredients of the mayonnaise(mostly oil, egg yolks and vinegar)separate when frozen and the result doesn't look or taste as good. The acidic nature of mayonnaise and the lower fridge temperature combine to form a very hostile environment for bacteria.

As far as easy to prepare sandwiches, I like either cube steak or similarly, ground round patted out about 1/8" thick and fried a minute or two on each side.

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Enjoy the music, not the equipment.