Thank you for such prompt and useful advice. I probably throw away 80% of all the egg white I buy and don't always have it in the fridge when I need it, so in principle finding a foamer with a long shelf life is a handy option. I shall try the Fee Bros. or Vegg White product.
I attended a tasting to choose a few cocktails for a wedding party where the anticipation is about 500 cocktails served during the evening.
The specialist ‘mixologists’ used this foamer in several of the proffered cocktails.