Like the others have said - it's totally up to you where you go, but I'll offer you a data point:
I regret not coming clean to my wife much more early on after my discovery of TTATT. I think it's probably important to take a few days or maybe weeks to really let it sink in, but it seems I entirely lack the skillset required to wake someone up if their connection to the cult is social and emotional. I had been in because of all the "proof" (which towards the end I realized the only thing holding me in was that they got lucky with 1914) and the proof that it was a cult was plenty to do the trick for me. So because of my inability in that respect, the year I spent trying to plant seeds was entirely fruitless and only damaged our marriage. When I "came out" to her at the end, it didn't go any better than it would've from day 1, and in a lot of ways it went worse precisely because I'd waited so long. I think if I had been open from the beginning I could've made it a somewhat more collaborative process of discovering whether it's the truth and even if I hadn't won her over that way, I think our marriage would currently be in a somewhat better place. Furthermore, since that happened I haven't had to sit through a single meeting, which is definitely a nice payoff. It's amazing how much more like yourself you begin to feel after being away from the mental stress of sitting at cult meetings.
It sounds like you've already eased into it and your wife is learning to come to terms with it in her own way. Not sure what your relationship is like, but in my case my wife was holding a lot of fear and distress inside and the uncertainty about my fate was eating away at her. At least now that she knows I'm destined for death at armageddon she can try to deal with it instead of being in limbo. It's possible that your wife might be doing the same, and releasing her from that, while initially painful, would be a kindness if that's the case. Since there doesn't seem to be any great risk of your wife leaving you, making the first move and being open and honest may actually serve you well.
Again, all this is said without any warranty, and is coming from someone that probably handled everything with his wife about as poorly as possible, so do with it what you will. I wish you the best of luck in whatever you choose to do.