I recalibrated by using the thermocouple on my multimeter.
That's not my biggest problem though - my biggest problem has just been keeping tips tinned properly. I've succeeded once, but it constantly feels like a struggle.
I found that brass wool works better at keeping tips tinned. A sponge removes all the solder and you have to quickly tin the tip immediately after wiping, otherwise it oxidizes. Wiping with brass wool leaves a thin layer of solder on the tip.
Also keeping the tip at moderate temperature range helps avoid oxidation - most manufacturers recommend to never exceed 400 C. JBC recommends to not exceed 370 C.
I recalibrated by using the thermocouple on my multimeter.
That's not my biggest problem though - my biggest problem has just been keeping tips tinned properly. I've succeeded once, but it constantly feels like a struggle.