Rachmaninoff's piano concertos reflect some of his relatively mature work. No. 2 was written at 28, No. 3 at 36. The popular Rhapsody on a Theme of Paganini at 61, less than a decade before he died

Chopin's two concertos, in contrast, were written incredibly early: both by 1930, when he was 20, essentially as his college graduation work. Most of the popular piano solo work, like the Ballades and Scherzos, came later. Chopin never wrote any more concertos

As a composer, Chopin peaked incredibly early. His early work and his late work sounds kind of similar. Instead of developing further as a composer, Chopin unfortunately died of tuberculosis at 39