Some people will follow up your application and call you 'out of the blue' even 2-3 years later. The mistake most people make is in expecting instant results. The general consensus is that it takes anything from 3-6 months for a translation agency marketing campaign to actually bear fruit in the form of work. The system may be a pile of papers, a file or a database - depending on the size and sophistication of the agency. If you can get 'on the books' of as many agencies as possible this will maximise your chances of getting work without having to go out and market yourself to direct customers.
Marketing is a numbers game - pure and simple.
The more of it you do, the more work you will get. Also the more experienced you get, the more 'feel' you will have for what actually works and what doesn't. Conventional wisdom also states that an email marketing campaign is even less likely to bear fruit. I think you ought to be aiming for much higher success rates. I wasn't the only one to get an excellent response rate.