When to take BBT?

Should you take it at the same time each day or when you've had a long stretch of sleep?

For me, it would be easier to take it when I slept over 3-4 hours than to take it consistently at the same time. That usually means anywhere from 1am to 2 am. Maybe 3am on some nights.

When my husband comes to bed (4-5 hours after I do), he moves around and snores a lot so I never really sleep to take it at say 5am every day.

My charts been wonky this month since switching from taking it at the same time (4:45am) to taking it when I feel I've gotten sleep.

Should I switch back?