Forum Moderators: LifeinAsia
In my case being on retainer is usually a matter of clients paying a discounted fee for a set number of hours of my time. So the amount of days/months varies according to the client's needs. Just be careful not to oversell your time or extend the time frame out too long.
Give thought to how you'll handle fluctuations in the workload. Some months you'll feel overpaid, other months you'll feel underpaid, but as long as things average out satisfactorily over time that's okay. You might want to have something in your contract that allows for extra fees in unusually busy times.
My retainer is more of an insurance policy. I'm there as a "fixer" in emergencies or when the instruction manual (euphemistically speaking) doesn't cover the situation at hand. It means their email goes to the top, phone calls are answered, etc.