I made some tests with a 5mm white led as load. I set the output voltage at maximum, then I reduced the output current to minimum and then I connected the white led and I increased the current to about 6.51mA. After about 1 hour and a half, the current through the led was 6.57mA. Then I touched the LM324, and the current dropped to about 6.52-6.53mA.
After this, I made another test. I disconnected the power supply from the mains voltage, then I reconnected it to the mains voltage. Then I measured during 1 hour the current through the led and it was initially 6.50mA and then it dropped to 6.48-6.49mA and it was constantly about 1 hour until the test was stopped by me.
Before these tests I made another one, with another amp meter and another 5k pot, and the results were the same.
Are the results of the tests good ?