Is it more important to take temp at the same time each day or after 3 hours sleep?

Hailey • 29 from Brisbane, having no. 2 (only 13 months after no. 1!)
For example I'll often wake up somewhere between 2.30am - 4am but then I'll go back to sleep and wake up again at 5.45am for work.  I usually take both temps but sometimes they're wildly different