Well mine are 19 months, and 21 months apart. I got pregnant with my second one when my oldest was about 10 months old. Then I got pregnant (OOPS!) with my third when my middle child was 13 months. We lost our very first one, at full term, so we were in a hurry to conceive after that, and it took us a full 8 months to conceive our (now) oldest son. But I honestly think it had to do with grief and depression. Our next two were very easy to conceive, but I was not on any form of hormonal birth control.
My sons are now 3.5, 23 months, and 2.5 months. They're really close together! I think it totally depends on you, and what you want as a family. And also, your health should play a big role in your decision making process. Some couples prefer to space their children 3+ years apart. I kinda wanted them close in age. I like the thought of being finished having children at a younger age. They make great playmates too. But I suppose it is easier when you give a few years between babies. So things are pretty rough for me right now! But it's what I want. These are the days I'll miss when I am older.
I don't have any experience with IUDs. Wishing you luck for when you decide you are ready for your next one!