I’ve got the gifts figured out, the party is all set. This is not a thread of desperation. She’s not freaked out about turning 40, but… what’s the coolest thing could I say to her on this occasion? Just some ideas. IOW, what would YOU say to an SO on such a milestone? I promise I will credit SDMB for the best ones. Anything goes!
You don’t look a day over 30, babe.
You are more beautiful now then when I married you.
I am the luckiest guy in the world.
and
You are fucking beautiful!
Of course! All good. I’ve got a few of my own, but it’s nice to inject some doper style, so keep 'em coming!
Your words should be from the heart and may be something like:
“You delight me with your love and you make my heart sing with joy. Thank you for the years past and I look forward to so many years to come. You are still the beautiful bride I married, and the beautiful woman I will love forever.”
Of course, if this is too corny, you can always say you will stay together forever and match wrinkles as you grow old together.
40 is just a number. There’s no difference between you today and you yesterday. Nor any of the yesterdays right back to the day we met - except each day I have spent with you has made you more beautiful. I love you.
Arrange to have her carded at the liquor store.
Good ones all. I especially like having her carded, though she has been and probably doesn’t need too much help in that department.
“Given how awesome you’ve been in your 30’s, I can’t wait to see how kickass you’re going to be in your 40’s.”
That’s what I’d want to hear, anyway.
This may be cheesy, but I love it.
Flowers and anything that says “you’re sexy, hot and I wanna do you right now”. Many women have the fear that 40 means “sexy-time is over”
Worked for me.
“No way would I trade you in on 2 twenty year olds!” 
Your’re older than any cat dog or horse! It’s just you and tortoises now.
These are hilarious. She will love them. The party went swimmingly, by the way.
Now today is when you tell her that she is now closer to being 50 then she is to 30. Which is very true–but when you put that perspective on it, well it is just turns the whole thing into a joyous occasion! I have that coming up here as I turn 50. So the next day I will be closer to 60 then 40 
But hey tell her to enjoy the 40’s as much as she can!
But if you do mention this to her—be prepared to run!
When you’re 50, you’ll look back on this day with fond memories…if you can remember that far
When the Lovely and Talented Mrs. Shodan turned a certain age, we were getting dressed to go out for her birthday dinner. She was looking at herself in the mirror in kind of a pensive way. So I put my arms around her from behind, and told her, “I loved what I had then, and I love what I have now.”
She muttered darkly, “Wait 'til you see what you’re getting next.”
Regards,
Shodan
If she lived on Mars, she could drink now. She’s 21 in Mars years.
You misspelled the title, the correct title would be “Help with Wife Turning 39 (Today!).” Of course, this means that next year you will have to start a thread titled "Help with Wife Turning 39 (Today!).