I always make it part of my night to capture darks, flats and dark flats at the end of every imaging session. You really don't need the darks if you have a set at the same gain/ISO, exposure time and temp but I find it just as easy to do them every night and place them with my lights for the night.
I must admit though that taking flats and dark flats with the wizard in NINA makes it much easier to do than it was with Sharpcap. But that is just my experience.
Telescopes: Celestron 4SE, Celestron 8SE, SkyWatcher 100ED Pro
Mounts: 4-5 SE, 6-8SE, EXOS-2GT with PMC-Eight
Cameras: ASI1600MC, Cooled
Tablets: Asus Nexus 7, Amazon Fire 7