Classes VS Job tracking

I work with non-profits and am trying to come up with rules for when to use Class VS when to use Job. My initial thought is that jobs are for one time events with a beginning and an end such as hosting a unique conference (or collecting information for a grant)  while class would be used for ongoing programs (kids daily swim) or departments (admin).  Having said that, I had the following questions:

If you have an annual gala as a fundraiser, do you set up a single Gala class, Gala class for each year or have a job each year? 

One organization allows other organizations to use their service for processing credit cards.  I am leaning toward creating a "Fiscal Agent" customer with a job for each event/organization. 

Thoughts?