I've only done maybe 2 12-15 hour Piety flicking Slayer days and that was to rush 85 Slayer from 80 before GWD came out but you've been coasting the top daily and weekly Slayer ranks so it would make sense in your case, friend.
It is a shame that pvp isn't as active as it could be. I partly put it down to the whole restart melarky, But it was the only fair way to do it.
+ can you imagine how many less people would be playing oldschool if they were able to xfer their maxed main stats to oldschool? especially before the gwd update. That would have been diabolical.
I also think it's why they haven't nerfed the xp/h at nmz.