Our group had some confusion about preparing spells for a Wizard and Cleric. The rules say that you prepare a number of spells from your list and that you tick off spell slots when you cast a spell. In D&D 3.x, if you wanted to cast a spell multiple times you had to prepare it multiple times, but we couldn't figure out from the rules whether or not this was the case in D&D 5e.
So can a spell be prepared once and then cast multiple times?
Best Answer
Yes. In 5e, prepared spells remain available as long as they're prepared.
From the D&D Basic Rules (e.g. from the cleric's or the wizard's Spellcasting feature):
Basically, 5e Wizards (and Clerics) are 3.5e Sorcerers who can swap out their "known spells" based on their spellbook (or godly mandate).
I can't speak to the exact reason behind the design decision, but I assume they wanted to enable a level of flexibility for both classes that was often lacking in previous editions.