Not sure, but I did manage to refine lvl 30 ancients during the 'event' (weapon + armour set) down to lvl 1, having strolls of 10 successes in a row (at the least) being no exception. Might entirely be due to the low-ish lvls though, but still.
The plussing didn't go that well though.
I refuse to buy most of those option stones as well. All I'm getting with the spare RPs are either the AS ones or the pdef ones (costing 9rps a piece) - which I then only use for 'special' occassions (such as actually grinding if I get my ass to it, or inter. dungeon runs where I'm supposed to 'tank').
It's ridiculous nonetheless, and I refuse to even try without the event. This probably also means I'll be stuck at 78-80 for a little while longer.