I think there are two aspects to this question.
1. How much current can the LED handle.
2. How much current can the PIC deliver.
If you take 2 identical LEDs and place one from a PIC pin to ground without a resistor, and the other directly across VDD/VSS and turn them both on ...
The one directly across VDD/VSS will glow very brightly, often with a different color than intended, as it heats up and burns out within about 20-30 seconds.
But the one that's connected to the PIC will shine brightly and continuously without burning out at all. It's lifetime will be diminished by some factor no doubt, but then I'm talking continuous ON current. With a short pulse at a small dutycycle, there's no way it can burn out, ever.
The difference is in the PIC output, which when presented with an over current condition, simply drops it's output voltage.
The PIC's temperature will rise slightly after a LONG time, but it's nothing like the LED across VDD/VDD which gets very hot.
For instance, an amber LED with a normal forward voltage of around 2.1V will actually drop the PICs output voltage to 2.1V, but it will only be delivering ~29mA.
29mA is not that far off from the 25mA max, so you really have a hard time getting "too much" current from the PIC's pin because the more you draw, the lower the voltage drops. It's almost like a constant current driver. 30ma +/- depending on the LED color.
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