These twenty 'Last Waltzes,' Op. 127 (D. 146), represent Schubert's mature exploration of the waltz genre. They are often more harmonically adventurous and emotionally complex than his earlier waltzes, exhibiting a profound depth of expression.
Mastering the subtle rhythmic nuances, expressive dynamics, and sophisticated harmonic language is essential.
20 Waltzes (Last Waltzes)(Op.127) (D.146) is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 6.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of 20 Waltzes (Last Waltzes)(Op.127) (D.146) lasts about 25 minutes.
20 Waltzes (Last Waltzes)(Op.127) (D.146) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.