Worried I wasted money on my new Moonlander, will I ruin my muscle memory?

I work on standard 104 key keyboards for my day job, but run an Iris Plus with custom keymap at home. I found that during the period that I was learning the Iris, my ability to type on a regular keyboard diminished slightly. I attribute this to the fact that for the first time in years I regularly had to think about what I was typing because I was learning a new layout. Once I pretty much had the layout memorized, I had no problem whatsoever switching back and forth.

It might have also helped that I wasn't typing exclusively on the ergo, so it may benefit you to practice on a standard layout every so often if you are concerned about slowing down.