Over the weekend my wife and I lost our air conditioning. I called a technician out to the house and he replaced both the fan motor and the capacitor. He also had to install a booster to help get my compressor turned over. I know this solution won't last forever but I was wondering how long my wife and I should have to be able to save up for a new unit.
Sounds like your compressor is dying. You are probably on borrowed time. Hard to say how long it will last, because it depends on how much the unit is running (depends on climate).
A total lifespan of 15 years is reasonable for a unit before major repairs are required.
Note that newer systems are usually far more efficient (SEER and EER ratings). And so they can pay for themselves pretty quickly. Especially with the tax credits that are available now.