Braces removal n Lip drop. In 5 months?

Hi,I am taking Braces treatment since 5 months and the doctor wants to remove it now. I am worried as it is too short span of time even though mine isn't a complicated case(No crooked teeth). Only front two teeth of upper row are a little forward.In these 5 months, he created spaces only in the upper row beside the front teeth and aligned them into U shape.Simultaneously braces on the lower teeth are put and the teeth are aligned(u shape) such that it wont disturb upper row. Now the teeth are aligned without any spaces and he says the bite is normal and hence can remove the braces. Though I am ok to wear transparent retainers for next 7 to 8 months as suggested by him, I am worried if my treatment will last max time without coming back to original shape.Is it ok to remove braces in 5 months? Also my lower lip seems to be a little drooping after the braces are put. Is this normal. Please suggest Thank You