I have been transcribing a number of 18th Century English wills and noticed that there don't seem to be mentions of wives -- at least not in the ones that I'm working on. Given the legal doctrine of Coverture (woman's legal rights becoming those of the husband on marriage), and the fact that the Married Women's Property Act wouldn't be until 1870, would the absence of such mentions be the norm or an indication that they'd already died?
I have only experience dealing with colonial American wills, but those should be under the same norms as English. I've looked at dozens of wills from New England in the 17th and 18th centuries, and naming the wife, when alive, was definitely the norm.
You are correct that coverture is an important consideration, but so too is the right of dower:
The widow was entitled to 1/3 of her husband's property when he passed for her lifetime or until she remarried. Some husbands would grant them more explicitly in the will, and others would describe which portion would become hers. In the majority of wills I've seen the husband left the wife explicitly the house and usually I also see stipulations that children must support Mom out of their own bequest.
Of course, there are always exceptions. One of my ancestors wrote a will in 1704 in which he doesn't name his wife of 56 years, who was definitely still living as she signed his probate documents. The judge viewed her absence from the will, along with the ambiguity in wording of the duties of the executor, as sufficient cause to doubt the will's authority and to nullify the will!