Given that HDDs are a lot cheaper than ten years ago (using Moore's Law, and a period of 18 months, that's 4641588 times bigger for the same price...), I would recommend you do any future rips to FLAC, and use MB to transcode to WMA in a parallel directory for loading to your Zune.
I'm lucky that I didn't start ripping until 2011, by which time, a 1.5TB HDD was a reasonable price, and I chose to rip to lossless FLAC, thus maintaining the full CD quality. A number of my friends are stuck with the 128k MP3 rips they made to save disk space, and can't face re-ripping...
Right on storage costs, captain, and mostly on your why-not-FLAC logic. But it's mostly a relative concern for phones because I have 2TB HD and a 256gb SSD on my main-MB NUC desktop. But still 320-quality is as low as I want to have on any platform, and I find that's plenty good for most music, especially because much of my listening in recent years is through Bluetooth. It's only especially-good recordings that merit the lossless ripping for me, and I believe I can only appreciate the differences on selected devices -not in my car's several nice speakers, for instance. I have 128gb cards in phones, and even that's plenty for my current ~75gb of music, but I also have a photo habit and do want to have plenty of headroom for all saving and downloading. But, still on your valid point, while storage is relatively cheap for all-FLAC, and will get cheaper, I still don't like wasting it, and I already have too many 64gb cards in desk-drawer storage. It's like my music players where 8gb, then 32gb, then 64gb became inadequate. Fortunately, we do have expandable phones and other devices today -except for iphone and pixel owners, that is.
Maybe one day
By the way, it's my Zune desktop software that can't read FLAC, and never could; but it does read everything else I've ripped with MB. Still. that only runs on Win 7, and the sun is going down on that as well. But/so I probably will be moving to FLAC, subject to some more testing and learning.
Finally, re-ripping was/is worth it and can be done patiently over time.