Hello,
my suggestion is simple : Instead of having time rifts opening on Monday-Tuesday-Wednesday-Thursday, please make it Friday-Saturday-Sunday-Anyday.
The purpose of this suggestion is to let us play Dungeons during weekends. Dungeons use up a log of sands of time per battle and probably most people (like me) can't play in the mornings or evenings due to daily routine.
Thanks for your time and consideration !