From this paragraph:
There are patterns of behavior that tend to indicate an impending life event. Looking for an apartment and working on your resume and upgrading from kegs of swill to four-pack microbrews, for example, might establish that someone is graduating. If your product or service could help someone at this stage in your life, your advertising to them is a mutually beneficial proposition.
I need to know what does this part of the paragraph means:
upgrading from kegs of swill to four-pack microbrews, for example, might establish that someone is graduating