Hmmm, so another week of Thursday daily:
Hard Mode: 2 drops x 3 = 6 Demon Crystals (8 stam used)
Normal Mode: 5 drops x2 = 10 Demon Crystals (6 stam used)
Don't know if it's just me, but ever since I started the game (I started on day 1, but the account I'm playing now started 2 weeks after launch since I rerolled

) - Normal Mode Crystal Daily
consistently gets better drop rates per Stam spent than Hard Mode every single time.
I can probably count on 1 hand the number of times I get a better return on Stam spent for Demon Crystals doing Hard Mode vs Normal, and that's coming from someone doing Hard Mode almost exclusively.
I know that drop rates for both N & H are supposed to be the same (60% x 6), but based on experience so far (never missed a Thursday daily if you count old account which I don't play anymore):
Normal Mode = consistently gets 4-5 drops, occasionally 3 drops, while 2 or less is very rare
Hard Mode = consistently gets 2-3 drops (3 being average, but 2 is also very common), occasionally 4 drops, while 5+ is very rare
Might be just my luck, but until proven otherwise, I think I'm going to stick with Normal Mode for Thursday daily from now on
Also awhile back there was discussion about there being no reason to hoard Sacred Crystals and that it's best to use them to roll Premium Gatcha.
Well, if you're a free user and never plan on buying SCs (or don't plan on buying much), then there's merit in hoarding crystals.
A LOT of merit, in fact.
The reason: Collection Events.
For example, the latest collection event in JP right now is for a Black Rarity Ninja, Nagi (a similar model was used for Liana's event btw, which was also a collection event).
To get CR and SL for the event unit, you'll have to collect an item that drops from the event maps (for this event, it's some sort of sealed paper - "Seals").
To get a fully maxed Black Ninja in this event requires 1600 Seals. The highest-tier map released atm gives 11 Seals per 50 Char/7 Stam spent. The event lasts 2 weeks.
Based on that drop rate, I calculated that for a Prince with level about 125 this is what you can expect:
Spend only natural Char/Stam regen on event + no SC = -1 CR, SL 3-4
Spend all natural Char/Stam + additional 15-25 SC = -2-3 CR, SL 5-6 (about equivalent of same rarity unit from gatcha)
Spend all natural Char/Stam + additional 55-75 SC = fully maxed out Black Unit
Not sure if we're ever going to get Liana's event over here now that she's in the gatcha. But if we get a collection event, then the average player will never be able to max her (or whatever collection event unit it is) without spending at least 30-70 SCs (depending on event and Prince Level).
Just something to keep in mind
P.S. Calculations above assume that you skip dailies - yes, even Monday - during the event.