I have thought about this some. I think the major issue here is that people on the Autism spectrum don't have the same need to constantly "engage" with their partners. So if you're at home with your partner, you don't need to constantly make small talk with them, ask them to share their thoughts, etc. In fact that might seem annoying to you. What matters is that they're there. So you might be unhappy they're away, at the same time you might enjoy a temporary spell of having the house to yourself so you deal with it OK. What's hard is having to frequently call them and engage in the sort of conversation that usually wouldn't happen at home.
Also, if the relationship is established, you really just assume the person will always be there for you. They're away, but they'll be back, so you don't dwell on it. You more or less (foolishly?) assume they don't need constant reassurance of your devotion to them, as you may feel you've already made that more than clear. Failing some sort of "red flag", you don't worry about that so why should they? They meet your needs for companionship, isn't that enough?
One problem that comes to mind is that Aspies can form a "theory" about their partner's feelings without discussing it. From direct experience, their partner is totally into them so what problem could there be? The problem is, this can change, especially if the partner doesn't feel they are getting the emotional feedback they expect from a relationship, but the Aspie partner doesn't see that, thinking everything is fine.
Considering the sexual aspect (as the topic is "partners" we can assume a sexual aspect to the relationship), the Aspie partner (usually a man) finds the sex satisfactory and has come to expect their partner will continue to be available for sex. In my personal experience, this can be a stumbling block if the woman is also on the spectrum, because those women (assuming they're essentially "straight") won't be as inhibited about hooking up with somebody else if such an opportunity arises; that doesn't mean they're ready to abandon the relationship but it's undeniably problematic. In my experience, NT women have a stronger personal commitment to monogamy. This is one reason that I don't consider relationships between 2 people on the Autism spectrum to be ideal, in fact they can be exciting at the outset but then one partner or the other simply loses interest, at least to some extent.
Note the preceding is a memory dump based on personal experience, I wouldn't be surprised if some people disagree with one or more opinions I've expressed.