When you boil hydrochloric acid it releases Hydrogen chloride gas and water vapor. Hydrogen chloride has a much lower boiling point than water. Therefore, after a few hours of boiling, you will have effectively boiled off a lot of acidity.
Also it might be useful to note that PH readings can differ with heat.
For your consideration.
"The real voyage in discovery consists not in seeing new landscapes, but in having new eyes." ~Marcel Proust