I made one intricate (lots of colouring and cutting) design for multiple (lost count) cards. Those cards are going to my best friends and favourite family members. For all the rest I'll make singular (no multiples), simpler cards. On the complex cards, I leave the sentiment blank and add it on at the last moment, so while every card is mostly the same, I will customize the sentiment. For example, for my former French teacher, it will have "Joyeux NoŽl" instead of "Merry Christmas".
To get over that "hump" of deciding who will get which card, I address all the envelopes first, and I will have an envelope out as I'm finishing a card, and then immediately match it to that person's/family's envelope.