Whenever I get an OLL case I know(I average 15 with 3lll), my OLL will be 1-2 seconds faster. OLL is definitely important as you get faster, I deeply regret not learning OLL and PLL earlier. I didn't start PLL until I was sub-20 and OLL until very recently. I could definitely be sub-14 if I knew OLL and probably sub-13 if I'd learned it earlier because I'd have had time to drill the casesI'm not sub 15 and I know OLL. OLL isn't too important to know because you can still know individual cases but do 2 look like you know what is gonna come next after you orient the edges. I don't recommend that at all but it is possible.