Yes, you need to replace your windows. I would bet the farm that your windows are lower grade windows. Look into a higher end brand that is made for efficiency. Look into okna windows and soft lite. These are made extremely well and are known for their air tightness. Stay away from anything sold at home depot, lowes, or local building supply houses. You will get nothing but garbage in spite of what some local jack off all trades contractor says.

Some condensation is normal in winter months, just keep that in mind. Your's are obviously due to poor windows.

Tony, did you have these windows installed? I'm reading mixed signals on that, as knowing that they are 8 years old suggests yes, but not knowing much other info says no?

If yes, contact the installer and have them come out to take a look. Even if they are not responsive, they can probably at least get you in contact with the manufacturer. Secondly, 40% RH if you are in a cold climate is excessive, particularly if you close window treatments to prevent the circulation of warm air over the windows. I am not saying that these windows do or don't need to be replaced, but condensation is an issue that has multiple factors and therefore typically requires multiple solutions to mitigate it.

Where do you live (regionally, for the purpose of knowing the climate)?

Is this 8 year old new construction, or an older home with 8 year old replacement windows?

How often do you have the blinds and shades closed vs open?

Do you run a humidifier (Aprilaire or similar)?