What symptoms or long term effects of stopping cold turkey 30 mg of Focalin XR have you experienced?

I haven't taken Focalin in a few years, but stopping any stimulant, whether it be Focalin, Adderall, Jornay, etc., almost always has an effect on the body. The reason is that your body becomes dependent not only physically but chemically. When you're put on a stimulant, it alters your neurochemicals quite a bit. From my personal experience, when stopping Jornay cold turkey twice in my life, I've gone through withdrawal. I wasn't psychologically dependent; it wasn't something addictive. It's that once you take something like Jornay or Focalin, a stimulant, consistently, your body naturally adapts, and when you take it out of that routine, it throws your body out of alignment, and it starts to freak out. I've experienced things like heart palpitations, increased anxiety, chest pain, and excessive sweating all from stopping my medication cold turkey. This is why a lot of times doctors like to lower the dosage and wean you off of it so this doesn't happen. I also have Postural Orthostatic Tachycardia Syndrome (POTS), so some of the heart palpitations I experience are due to that, but one thing I will say is stopping my medication cold turkey made those palpitations more frequent and more painful. I'm not sure if there are any long-term effects, but my symptoms from stopping the medication lasted 2-3 months in both instances.

Still taking it so no personal experience but these are the potential withdrawal symptoms. Sleep disturbances, depression, apathy, changes in blood pressure/heart rate, anxiety, and restlessness. Physical symptoms might be teeth grinding, sweating, severe weakness, fatigue, and seizures.
Focalin XR withdrawal symptoms generally last for one to three weeks.
I'm sure you've heard it or read it but do not stop cold turkey. Get a tapering dose schedule and withdrawal timeline from your doctor.