I am probably one of very few people that have so many pots without drainage holes. But.....I am also one of those plant growers that water seldom and I mean seldom. In the summer when it rains and if I see too much water has collected in the pot I just tip them and they drain. Indoors my house plants may get a drink once a month, most times it is every other month.
I grow succulents in pots without drainage holes and have never killed one. The only plant I have ever lost is from not being watered.
This plant is in a pot without holes. It has been in this pot for 4 years. It has gotten so big you can no longer see the pot. It is a plant that seems to want to be moist at all times. If it dries out the leaves start to crispy.