The degree of swelling that occurs after gynecomastia surgery will depend on the exact procedure performed. For example, swelling tends to be greater with larger areas treated, especially with liposuction surgery. Generally however swelling should subside and you should see your final results 3-6 months post op. Occasionally, again depending on exactly what procedure was performed and factors such as skin elasticity, results may improve even up to one year postoperatively. Best wishes.
My general observation over twenty five+ years is that for the majority of my patients (it varies from patient to patient) that you will have about 85% of your results at 3-4 months and final result at one year.