It will be a dark day indeed if I get a duplicate black unit, the choice to throw into my main or sell will be hard. Though I feel like selling would be the better option though I know I wont feel good about doing it. Just look on the bright side, it is for the greater good!!!
CR/SU guaranteed would be MUCH better use for a black if you're not going to use 2 copies, unless you're never going to use said unit's first copy. I honestly don't understand why people would even sell their 3% chance lucky draws unless said lucky draws are units they've already CR'd and duplicate usage is inadvisable (like Deine, god that cost says NO to using a 2nd copy), IMO the RCs are a means for whales to use their spare gold and less useful platinum units for something other than mini-plat armors, not something you'd throw an ultra-rare unit away in favor of PART of the cost of another unit that you're guaranteed to get if you play (or whale) long enough.
For a certain population of players getting rid of their one and only copy of a plat or black isn't that strange. There are units you absolutely wouldn't use on principle even if you had access to them; like Aisha. 400 RC right there. Don't care how silly powerful the unit is. She looks like an 8 year old loli with terrible art and asking 400 RC for that feels like more than it deserves.
Eh, like I said, it's OK if you're never going to use the unit's first copy. If they want to play with such self-imposed restraints, that's their choice. Aisha is ridiculously OP but I understand there are some against lolis. Me, personally? IDC what the unit is like in their scenes as far as using them in battle. If you're OP you get used even if I don't like your scene. If you're weak in battle but I adore your art/scene, you're in the barracks where I can re-watch your scene to my heart's content <3
oops. I was thinking you get 15 from event plats but it's 3 so without spending SCs you should be able to get 30 from a farm event if you don't want the unit. Actually now that I look at it, I haven't used any of the farm units from this year and all the farm units I used from last year I stopped using.
However my overall point still stands. Slow and steady and you can get him or any others they add (DMM has 2 1000 and 2 400 RC units I believe).Gold rush could be a big bonus as well. They give the full 20 and you can get many dupes that have little value.
these rainbow cristal will stay around or only for limited time?
No, its permanent feature.
I prefer to have only one of each unit, I don't use duplicates as I feel like making each unit special and having duplicates takes that special feeling out of each unit. I am yet to get a double black yet so now sure if I will discharge or add to my existing one. Only black I have currently I don't use is Berna, I have plenty of other rouges to take her place and haven't needed a black rouge's power to deal with any missions yet, so if I did get a double of her I would most likely sell it no hesitation, though if it was one I do use like Sybilla.....I might consider CRing.
I believe these are a permanent addition like Demon Crystals, it is just a new way to shop that benefits pay too play players more, free player can still use it they just wont get the Rainbow Crystals as fast as those discharging their doubles they get from their runs at the summoning shops.
There's quite a number of units whose Skill Awakening changes them drastically, yet their normal skill being just as good. In these cases it makes perfect sense to keep dupes around with intention of SAWing one and keeping another with regular skill.