Is it normal for your "period" flow to not change while on birth control?

before birth control my periods were never very heavy and lasted about 5-7 days. I've been on my combo birth control pills (Tri-Cyclen) for about a year and a half and the flow during my withdrawl bleed has basically stayed the same. I still bleed for approx 5-7 days. My flow starts heavier then tapers off to a medium then light flow which is how it was before bc. the only difference is now I don't get bad cramps. I always hear people saying that their withdrawal bleeds are a lot shorter and lighter. Is it normal for mine to stay the same?