Hey Ruth-
Yes, other races are important IMO. Of course those are much shorter, but I think they help.
Here is how my life works around IM. It may or may not work for you.
I live in a crazy climate, so when most of the country is racing, I'm struggling to get a workout in before it gets too hot. But here is how it works for me.

Jan- April is my peak build for Ironman. I generally do not schedule much of anything on the weekends due to the fact that I need to be on the bike for a long day every weekend. I "plan" it this way knowing that there will be at least one weekend I'll miss due to something. But I'm pretty anal about my IM training. It is the most important time of the year for me.

After IMAZ (now) I will rest for a week. I'll do NOTHING. I need to let my body recover. And then I will slowly ramp back up to a nice normal training schedule. But this takes about a month. It is crazy how fatigued you are after an Ironman. I already took a nap today! And I took a two hour nap yesterday. I also noticed last year that my body was good for no longer than a 45 minute training session for the first month post IMAZ. But I won't push it.

I do have a sprint tri on the radar for memorial weekend. I'll also do some other smaller races in so cal over the summer to keep me in good form. I find that keeping a race in the schedule gives me something to train for, and keeps the tri vibe going. In october I'll do the Subaru womens tri again (since I didn't get a kona lottery slot) and I think I'm going to do SOMA half IM in October.
November and December are always hard months to keep me focused. I just want to bake cookies and enjoy the holidays, but I have to keep my base up, because come Jan 1 I'm back in the IM saddle. But I will admit it's a struggle, and I don't put too much pressure on myself because I realize that my body/mind needs a break every once in awhile. And if you don't take a break you will get burned out.
Anyhoo... thats how I roll. Hope it helps.
Cheers!
Denise