I went through this a few years ago-both my wife and I went into "competitive" fields. I understand that you are not in the mindset to interview at a ton of places, nor do you think you can afford to. I felt the same way.
Unfortunately the consequence of not matching is pretty bad, and you need to do everything you can to avoid it. It is a lot of money and time, but they are a drop in the bucket compared to what you have spent and will spend on your career in terms of money, time, and sacrifice. Where you match is a big deal, and my guiding thought was to make sure that no matter what happened, we could look back and say we did everything we could. With that in mind, here are my thoughts:
You both need to focus on cities that have multiple programs for each of you.
The applicant for the competitive specialty needs to interview everywhere they can.
I would argue that the applicant for the non-competitive specialty needs to interview almost everywhere they can as well for the following rationale: Lets say you knew where the competitive specialty partner was going to matchwouldnt you interview at as many places as you could in that city? It would give you a better chance of matching and more options in the program or type of program you are in. No matter what youre doing, thats at least three years of your life. The problem with the match is that it really could be just one program that your partner is able to match into (especially if it's a competitive specialty) and you don't know which program it is. Approach the interview season as though you are applying to a competitive specialty. In a sense, you are--your partner's. You can hold it over their head for the rest of your lives.
If I were the applicant going into the non-competitive field, I would NOT push all of my interviews to the end of the interview season for the following reasons:
1. You may run into scheduling conflicts if you cram them in at the end and then need to change dates or add interviews later. You just don't know what is going to happen.
2. It's nice for the competitive-program-applying partner to say I am couples matching, my partner already interviewed here (or in the region), and they really like the program during the interview day.
3. Going on a lot of interviews within a short period of time is exhausting.
4. In general, I think it just gives you more flexibility and comfort to know what youre dealing with early on, rather than waiting until the very end and having it all come together at the same time.
If you're worried that the schools are going to forget about you, or think that your partner never interviewed in the region, I think it would be appropriate to send them an update letter when he/she does.
Having said all that, I understand not wanting to go on every single interview. It feels like a waste of time, and its certainly a big expense. My wife and I were each cancelling interviews by the end of the season.
So heres what I would do:
Schedule some of your interviews early in the interview season. Focus on high-yield regions (regions with multiple programs for your partner). This will probably end up being cities like Los Angeles, New York, Boston, Chicago, and a few others. Put those interviews closer to the beginning of the season, and put low-yield regions (regions with fewer programs for your partner) towards the end of your interview season.
You may be contacted by programs and told that you are "ranked to match" or "they would love to have you" or something similar. I cannot stress enough that you CANNOT believe them. It is nice to hear, and it does suggest that your chances are good, but it is not a binding contract and you should take it as a compliment and nothing more. I personally know multiple people who were told they were "ranked to match" by one program and matched elsewhere despite the fact that they had ranked that program #1.
You may have logistical conflicts that force you to choose to interview at one program INSTEAD of another. Know where your partner has applied, where they have been rejected, and where they have been offered interviews so that you can quickly respond to interview invitations while taking your partner's interview status into consideration. Available dates fill-up quickly, especially for some of the competitive specialties. Communicating with your partner and staying organized is key.
When would I cancel interviews? I would cancel an interview if my partner did not have an interview in that region, or I had already interviewed at multiple programs within a given region and felt that my chances of matching there were high.
You will spend more time and money during the interview season than you want to, but you will get through it. As bad as the couple's match may seem, it's not nearly as bad as it would be if it didn't exist.
Best of luck.