Yeah, vol is important, but too much will kill you if you aren't truly market neutral haha. By HF realm, I assume you mean High Frequency not High Finance. Yes, HFT folks are very quick to adjust, I understand that (at least at a particular firm) the shelf life of a strategy is in the weeks to months to years if lucky. You were achieving pure arbitrage, as in crossing the bid and offer on multiple exchanges? If so, please PM me so we don't drag this thing too far off topic.