Normally you would need your coolant flushed every 1-2 years. I'm not sure on the details why it was recommended to you to flush it twice last year. If you are loosing coolant and refilling frequently, it's important to make sure you have a 50/50 mixture of antifreeze and water for proper cooling of your engine. There may be many reasons why your coolant has become contaminated and requires frequent flushing. That is best discussed with your technician who regularly services your car. Or seek out a local experienced technician who can best advise you.
uhh you dont have to flush it that often..i would say every 40k miles..if its dirty after a few months or even days..i would be worried about corrosion in the block or radiator..or water pump..if its running funny and u are overheating..or losing oil..check ur head gasket