A little background first:
We have been married a little over 20 years. I have been wearing panties full time since before we got married. Early on, I put on a garter/stocking set that I had bought her, but she would never wear. She got upset & it was clear that panties were the limit. I kept my dressing hidden after that.
I have never been interested in trying to pass as a woman, I just like wearing the clothes. I don't wear wigs or makeup. I dress as a "Man In A Dress".

About 5 years ago, I started wearing night gowns, which went OK.

About 6 months ago, I gave her a book "He's the Maid", which details how a wife can train her husband to be her maid...complete with uniform suggestions & everything. When she finished the book, I asked her what she thought. The conversation went like this:
"So, you want to dress up in women's clothes & clean the house?"
Yes
"who is going to get the uniform?"
I will take care of all that
"OK"

So, I put together a French Maids outfit, with stockings, garter belt, thong, bra with forms, petticoat, & a short French Maids dress. I have been cleaning the house in the uniform once a week since.
I have since brought out a few things from my stash, mainly a couple of skirts & a couple of bras. I have worn these a few times around her, either skirt, or bra, but not both, & only for a short period of time.

Now for the Milestone:
Yesterday, after I finished my cleaning as the maid, I got out of my uniform. I only took off the dress & petticoat, leaving on all the undies. I put on a long, flowery skirt & went into the living room wearing the skirt & bra, but no top. My wife looked up from her book & I asked her: Do you have a top I can wear with this skirt? She got up & went into her closet, with me following. She went to her tops & turned & asked me "what did you have in mind?" I told her I wanted something that matched the skirt. She pulled out a few tops & we discussed which would go best. We decided on a short sleeve orange blouse with decorative piping. She handed it to me & went back the living room to her book. I put on the blouse & went to the living room & asked her what she thought. She looked up & said "that matches well", & went back to her book.

I went about the rest of my day. We fixed & ate dinner, then retired to the living room & watched TV for the rest of the evening. At the end of the evening we went to the bedroom. As my wife was getting ready for bed, I took off the skirt & blouse & hung them in their places in the closet. I took off my bra & forms, stockings & everything else & put them away. I put on my night gown & we crawled into bed. Nothing out of the ordinary was said. It was as if this was our normal nightly routine!