Thanks Robert. 90 seconds is about as far as I'd go with this setup currently, but the keeper rate drops. 60 seconds seems to be a spot where I keep about 85-90% of images, which I'm happy with.
Definitely looking at auto-guiding though!
Yes I felt like a fool when I got home and realised I forgot the flats
the OTA was still locked into the right focus point, but I'd taken off the camera. I've no way of knowing which orientation it was in to align the sensor to imaging circle.
Oh well, lesson learned. I might start taking flats before the imaging session going forward.