That depends on your mastery of the Force, [member="sabrina"] . Telekinetic lightsaber manipulation is a tricky thing, especially if you start using lightsaber forms in conjunction with that. Imagine the mental strain and mastery required to use one lightsaber with your hands.
Now imagine the strain of doing that only with your mind.
Now multiply that strain by how many lightsabers you want to control at one time.
And then if you want to perform techniques and/or forms, you have to think of all of those moves individually per lightsaber.
And then if you use different forms per saber, that adds even more strain
Theoretically, with full TK mastery and specialisation, you could control as many sabers as you want. The problem lies in the complexity of the telekinetic saber use. It would also require intense concentration to do anything more complex than simple, repetitive movements.
So while it can be done, and in excess, if you go overboard you'll probably fry your brain.
TL;DR~
As many as it takes for you to get reported, then take one away.