Also, see if you can figure out what your sleep cycle length is. For most of us it's somewhere around 90 minutes, roughly. It's easiest to wake up between sleep cycles rather than in the middle of one because we sleep most lightly at the beginning and end of a cycle. You can feel refreshed and alert waking after a while number of cycles even if you still need more rest. Whereas waking mid-cycle feels miserable and groggy even if you technically got more sleep.
Once you figure out your sleep cycle length and how long it takes you to fall asleep (8 hours is 5 90-minute cycles plus 30 min to fall asleep), you can work out how long you need to stay in bed to catch up on sleep. Adding a fractional number of cycles won't help much, and you'll feel groggy again upon waking. Adding a whole number of cycles will help you catch up and feel rested.
Since you're married, can you and your spouse take turns crashing at 6pm for a couple weeks to catch up? It might also help to sleep in separate beds when you're extra tired - sharing a bed with someone whose sleep cycles aren't perfectly aligned with yours can interfere with sleep. Other tricks can help with that too - such as getting separate blankets.