I am drying in my growtent, humidity is about 60 and temp is about 19c, I am running my extractor on a lowish level (about 30% of full power) for 15 mins out of every 60.
Is this about the right amount of extraction?

Personally I ran my extractor (through a carbon filter) at 100% when drying.. You need to get the mosture out of the room to prevent bud rot and mold from developing.. I also ran an oscilating fan in there too (pointed at the floor - not directly on the bugs) so that there was air movement..

Had no issues with any rot or mold even on the fat buds.. Personally I`d rather have my bud too dry before stick it in jars - its easier to hydrate (bit of apple in the jar) than to bin moldy bud

Yep,

The most I do is turn it down, I never turn it off.

Thanks guys, I have it on continuously now. I still have it lower than I would use when growing in there though. I will keep an eye on it