The Dutch Iris come back every year, I have had some of them nearly four year I think now. I have added others along the way. I don't dig and store the bulbs, I just leave them in the ground and mulch them through the winter.
This has been the worst year for them as far as blooming since I have had them. It may be because of all the rain we have had this year, I don't know. I might need to check into it a little further and see what other causes there might be.
The Mexican Sunflowers will reseed and come back. I made a big effort last season to control the seeds and seedlings throughout the season and into the fall, and this year I had none to return. I had bought so many new plants I was not going to have room for them this year.