Watched over two successive nights so it didn't seem too long. It is very slow and intense paced with occassional bursts of action. Very much the style Leone pioneered or brought to the fore with the spaghetti westerns. 

Elizabeth McGovern is far too baby faced to play the older 1960s Deborah when she would be over 60. De Niro and Woods and the rest of the gang and hangers-on manage the transistion from teenage/young men to the 60s ok. (we know they were all born in 1905 ish from gravestones). This rather mars the closing sections. They are all played by different child actors as young boys in the 1920s.

The cutting between timelines is sometimes confusing. I didn't get the final twist until near the end, although it is telegraphed early on.