Can persist for yrs
by itself is with us thru out life.
If you can burp/belch/spit up then you reflux. Reflux disorder or disease implies important negatives:pain, weight loss, etc. Upright posture after meals helps most of us avoid sx. As long as babies feed often and lay flat, gravity is not helping keep the food down & they may have sx. I've had a rare baby on meds until 4y, most are off by 6-9mo.