I would not worry about the shelf life of pre-catalysed 2-pack aerosol. When its used its vastly inferior to a decent two pack system. I tried some from Jawel which they preload into cans after matching the colour. (How many shades of white do you think there are?) They do warn you its not as good as a proper paint system.
Why not invest a little money in a portable compressor, an airbrush and some decent paint? Its not too expensive and its there for use for the rest of your life.