I read that if multiple strips are connected to the same pin, mirroring each other, the data signal from the mega will slowly degrade across more and more strips, leading to strips not lighting up in the right color correctly.
I am not using any resistors on the data wires as suggested by the Adafruit website
I am currently not using any signal buffers to buff the signal coming out of mega
My project right now involves ~6000 LEDs and maybe more
No this is incorrect, The data signal is regenerated when passing through each LED so there will be no effect of the signal slowly degrading.Why not? It is just a resistor. Try one resistor on each of your panels. No need to, unless the Mega is a long way from the panel. In this context a long way is in the order of about 3ft.The mega does not have enough memory to cope with more than about 2400 LEDsYour problem is more likely to be the power supply and how you have wired it up.
If the same color is sent to all LEDs, no memory is tied up.Each strip needs power applied to both ends and possibly in the middle (depends how long they are).To make a buffer, use some chips like 74AC244https://www.digikey.com/product-detail/en/texas-instruments/CD74AC244E/296-32957-5-ND/1691809with the inputs driven by the Mega and the outputs driving the WS2812B strips.Put the 'AC244s close to the Mega and keep the wiring short & neat.Then you can have multiple strips connected to each output, experiment with quantities and see where it stops working reliably.
All the strips are connected in parallel, both as in power and as in data. So Im sure the power is not a problem.
to believe that the constant "splitting" of data causes it to degrade.