I have a FS and have montly ultrasounds now, mainly because I'm on medication and they want to see how it is working for example is the medication helping me ovulate on time and how many eggs has the medication made me produce. I also take a montly injection which means I time the insem for 36hrs post injection. For me I find it a whole lot easier because I'm trying to coordinate my O with a donor so need to be as precise as I can. If I wasn't working with a donor and didn't need medication I probably wouldn't have the ultrasound, I'd just use a fertile window.

CGB - In terms of the "working order" you mentioned I found out I wasn't in optimal working order by Temping. From temping I found out my O was later than ideal and my luteal phase was short which resulted in me seeking treatment. My family history is very, very fertile so I got a big suprise to find out I have some problems. So family history isn't always predictive of your circumstances, but I understand your concerns.