When Do You Call It Quits and Call Your XPS 13 A Lemon?

I have been a loyal Dell customer for many years – buying computers for my family and for my business. I buy new computers every year to regularly replace computers - to keep my systems current. Now, I have a XPS 13 (I replaced an older XPS 13) that has been nothing but a nightmare of an experience for over 6 of the last 12 months. Today, I’ve had to ship my computer off to Dell to repair. I currently do not have a computer to use! I am totally disappointed to a point where I am thinking of discontinuing ever buying or recommending Dell computers for my family, my business, to my clients and associates. My question is at what point does Dell call it quits and call a computer a lemon and replace the system? They have already replaced most of the major components (hard drive, battery, modem, memory, reset the system twice, reloaded the operating system, etc.) At one point, the supervisor that I spoke with assured me that everything was going to be alright as they were replacing so many parts that nothing would be going wrong. Being so frustrated at that point, I asked at that time about replacing the system due to this computer being a lemon/problem system. She assured me that if there were any more problems that at that time they would replace the computer. Well, my computer is having another problem (cannot connect to the internet) and so much of a problem that I had to ship my computer off to Dell to repair. This problem has been going on for over a month now. They have wasted a lot of my time, I have not had the full use of my computer, I’ve lost a lot of my data, Dell has spent a lot of their time and money trying to repair my lemon and Dell has yet to repair my computer. So, back to my question, at what point does Dell call it quits and give me a system exchange? In all my years of buying Dell computers or any computer, I have never experienced the kind of total failure that I have experienced with this one computer. Yet, Dell representatives/technicians/managers insists that everything is ok and they will repair everything. The continuing problem is that they don't understand that I'm the one who is suffering through 6 months of problems as I don't have 100 percent quality use of my computer.