What seems reasonable to you as a spouse if your request for married intimacy is refused is very personal and unique to you as a person and your marriage. Other couples will have different ways of communication about this and different ways of addressing meeting each other’s needs. That is all fine.
What I was asking about before, was your point 1, which used the term arbitrary, right? I understood that to mean without just reason, because when we say someone is making arbitrary decisions or is acting arbitrarily, we commonly mean that person is placing themselves above others and is not taking into account the concerns and needs of others. So that is why I asked, and perhaps you meant to use arbitrary in a meaning different from the way I commonly hear it used, so my reservations about your point 1 were unfounded.
Suffice it to say, if spouse A believes that their spouse, Spouse B, may say “I don’t feel like it right now, honey”, with no other talk of why or how long of postponement, and that is considered fair and reasonable, then there is no concern about unreasonable refusal.
If, however, spouse A would feel rejected by Spouse B if such a refusal was made, especially in situations where this happens frequently, then there would be a concern about unreasonable refusal and it would be grave matter. In situations where getting rejected is possible, it might be good to employ a few strategies ahead of time to avoid causing emotional injury to the spouse. Perhaps establishing a ground rule that requests will not be made if one spouse is ill or injured, but that offers for married intimacy are always acceptable? Instead of imposing an obligation on an exhausted spouse, an offer for an opportunity for them to receive love and satisfaction might sound more appealing. Then, specific requests can be reserved for times when one spouse or the other really needs the physical or emotional comfort of the marital embrace (like say, if they feel downtrodden or plagued by unlooked-for temptations). This is just one idea for how to address the issue in a marriage where saying “I don’t feel like it right now” might be perceived as rejection. I am sure there are millions of other ways to communicate about this carefully.
Spouses give over to each other the right to marital intercourse when they wed, so both the requests and refusals need to be reasonable and always considering the other’s needs before than one’s own. The reasonableness depends upon the manner and frequency, as well as a host of other important considerations, and is wholly unique to each couple.