I like how you planted the seed in your wife's mind about how crossdressing is a great way to relax, re-open lines of communication and 'keep check' on how your testosterone manifests itself.
I do that's a nice way to introduce the concept.
It may be very easy for you, at the end of the 45 day period to say
"Y'know honey, I never expected it, but Ive actually quite enjoyed the last 45 days. More so, I love how much closer we are blah blah blah, I think I might keep my girl stuff to wear on a more regular basis"
Wife assumes that the 45 day trial got you hooked and her encouragment and positive commentry gets you off the hook with that in some respects.

But seriously, you're getting a second chance with your wife?
How about just giving her the straight forward truth?
Or is that a dirty word?
Many of us will have lied and regretted it (myself included) the lies are usually motivated by fear of losing your partner due to rejection of your newly admitted trait (I know mine was). But those of us who did lie know how much worse the lie is than just being honest from the get go.

Take it from me, just tell her the truth.
If she stays, she's yours.
If she leaves then it was never meant to be.