I've been reading about planting different varieties of bulbs in the same area at different depths. Everything I read says it works fine for the usual spring bulbs (daffodils, tulip, crocus), though the area I'm planting the main focus is on lilies, I have mainly different orienpet bulbs, although I do have some asiatic lily bulbs to plant as well. My reading seems to suggest that I can do daffodils and tulips in the same area where I've planted the lilies (at different depths), although I'm wondering if it would be possible to do other bulbs like allium and iris (I know they aren't really bulbs, but still) in the same area.

Is there a downside to doing this, other than the fact that they might have to be dug up eventually to divide them? I'm thinking that irises are too dense for the lilies to come up through and would be too much competition maybe?