My most recent HDL cholesterol level was so so. How high can HDL go?

Hard to tell. As a lipidologist i often get referred interesting cases, most recently someone with an HDL cholesterol level of 168. This patient was a high absorber of cholesterol in the intestine, with very high levels of a protein called apo a1, the building block of HDL cholesterol . While her total cholesterol was high, and hdl, everything else was normal. These can be confusing cases. See a doctor.
I've seen 125. The highest hdl-c i've seen is 125 mg/dl. I've seen many just over 100. Optimal is over 40 for men and over 50 for women. Over 60 is considered very good.