Should I stop worrying about his wife finding out about us now?

For a couple days there, she was consistently going through his phone and only going specifically to the app we use to talk to each other. He only uses that app to talk to me, and when he has to go back around her and their kids he locks and hides our chat before closing the app. He doesn't go back into the app until he can talk to me again, and I know this because the messages I send while he's gone stay at undelivered until he opens the app, and then go to seen when he unlocks and comes back into our chat.

I'll list all the instances that she's recently been into the app. She can't access our chats directly, but he's told me when you go into the app you can tell when a message has come in, you just won't see it listed on the main page.

March 1- she opened the app around 6 AM (he was asleep and didn't realize she had gone through his phone because she puts it back exactly where he leaves it, but I could tell on my end)

March 2- He came home around 12:30 AM from being out with friends (we video chatted on his way home). When he comes home he sets his phone down at the entryway. She opened the app within the hour after he came home.

March 3- He came home around midnight, we were on the phone as he drove back. She checked his phone less than 10 minutes after he came home. It was after this time in particular that he for the first time said he could tell she opened the app.

She hasn't checked since then, but I think that has more to do with the circumstances around his coming home. For the last two nights, instead of coming out of the car since they've been at each of their parents houses visiting every other day, he picks her up so there isn't an opportunity for him to set down his phone. I also noticed he didn't even open WhatsApp (not the app we use) at all so I think he's avoiding using his phone all together around her right now.

But maybe she isn't checking because she's off his trail now and I shouldn't be worried? I think he's really good at lying to her, otherwise how could we be having an affair for so long. I guess I'm asking what your opinion is on this? Does it sound like I should just stop worrying about it? Or does it sound like we have to hide better idk