So I figured out why the last week or so hasn't been working for us. I've been responding to the girls too quickly!
Today, they woke up after a half hour and I rolled my eyes and decided, screw it, they're fine, they don't sound unhappy, they can just sit there until either I finish my lunch or they start sounding upset. I looked at the monitor when I finished my lunch and they were asleep again! They were asleep for another solid hour!
Duh! I can't believe I've been stuck in this cycle of only a half hour per nap when if left to their own devices, they would sleep for about 90 minutes.
This feels like the moment when I discovered that Tina will resist sleep for as long as she knows I'm around, but if I leave completely, she'll nod off quickly. I felt like a horrible mom when I would step outside to clear my head because she wouldn't go to sleep in those first months until I realized that me being outside for 5 minutes was more productive to her sleep than me trying to soothe her for an hour.
Well now apparently me going to get them as soon as both are clearly awake and chatting with each other isn't the best move either! I felt like a real jerk today making them wait for a while but I guess it's what I should have been doing all along. I bet they'll be awake a lot longer before showing tired signs now that they've taken a long nap.