Hi!

The current leaves will always stay as they are (they will not suddenly develop more holes). The holes in a Monstera are created with age, light, and ability to climb.

The less light the plant receives the less holes it will have (that being said do not give it direct sunlight). A bright location is best for fenestrations. If given a stake to climb the leaves will both get larger and have more holes, usually this helps it to also get the second and third sets of fenestrations on a leaf.

I hope this helps. It’s a always fun to see what a new leaf looks like and how many holes it has!

The number of fenestrations any leaf will have is determined as the leaf develops. It won't gain or lose any more of them. If you want the new leaves to get larger as your plant gets older, then give it lots of water in a fast-draining soil, along with lots of bright indirect sunlight. This is why mine goes outdoors as soon as the weather warms up enough for it to do so, and it responds by growing like a weed. But for now, it's staying in my bedroom, where it brightens up these cold, dreary winter blues.