I probably shouldn't do this but I'll keep slicing as long as its landing on something useful.
Raw Offense/Protection/Health (This is how I end up with a 3500 Protection Mod that is still Speed-3) Grrr.
If it lands on Health/Defense % then I'll probably stop.
I also tend to just ignore slicing on a mod even if it has speed if I'm seeing the other 3 stats and at least 2 of them aren't "good" stats. I'd like to get something useful even if it doesn't hit on speed.
A friend is different, he upgrades greys to 12 just to see if speed shows up but the minute it misses landing on speed once its shown he stops leveling/slicing it.
Me, unless its a "rare/good" combo from the right side of the mods box, I don't even keep Greys.
A Grey Square/Diamond/Circle at L1 just gets sold immediately for cash.
I don't start leveling them till I see Green w/ Speed at L1 if its a "Left Side" mod.
I'm less restrictive w/ the Arrow/Cross/Triangle slots since its more about the Primary Stat, in a lot of cases, than it is the secondaries.