I don't think they're worth saving on the off-chance of there being an event for it. They're relatively cheap and obtainable in a lot of events. I'd rather go ahead and obtain the power boost from them.

yah, we will need it, i want event purify. from that event giving us the low % is 60%. and the higher is 99%. from that event we not need use purify protect if want safe some stat, its better cos much ppl not have much coupon and ingot for that. .
some event is good if make all ppl happy with cheap price or good event, but i see the last cheap price isa oct 2016, from dec 2016 all become expensive from exchange pt ;P