I use interplanting a lot, mainly for efficiency. Here, taken February 19, are onions and lettuce interplanted with cabbage. When the cabbage needs the room, the onions and lettuce can be harvested. I have sometimes left the lettuce and onions in place and I still get big cabbages.
Usually I just put lettuces between the cabbages, but this year I was out of room for the onion sets. The cabbages, lettuces, and onions seem to be coexisting quite well.