I bought my SSD about 18 months ago.
For a couple of months, I kept certain docs on the SSD, on the assumption that might help access speed.
As it turned out, keeping docs on both my SSD and my HDD complicated my backup strategy, so I gave up and put them all back on the HDD.
But I do recall being underwhelmed by the improvement. Hardly noticeable in my case.
Not to mention the size problem---my SSD would hold only a small fraction of my total data---although ALL of my "docs" (text files, Word, Excel) would have fit.