I know it's too late to say this because the cycle is well underway at this point, but I suppose it's advice for next year.
This is my first time on a search committee. I work at a primarily undergraduate institution that cares about research, but is teaching-focused. I've been reading the applications for a search we have underway and I have to say I'm underwhelmed by the cover letters. Most of them are generic, a half page or a page long, and basically reiterate the first few lines of the c.v. without mentioning aspects of the job that are clearly written in the ad (i.e. no mention of how the candidate fits the job.)
I know people get horrible advice on cover letters which is why so many of them are this way, and I also understand that research universities might not mind this kind of cover letter. So I'm willing to give people the benefit of the doubt. We haven't had an official meeting yet as a committee, but at least one person I've talked to feels more strongly than I do and is unwilling to give these people any benefit of the doubt.
So, I'm just putting this out there — please customize your cover letters. If this means you must go over a page in length, fine, make it two pages. But I think you can do it in a page. There is no need to include details of your training when it is literally the first section of your c.v., which is always the other thing that search committees turn to first. There will be people who are unwilling to read past the c.v. and cover letter if one of those is not up to standard. Don't get screened out just because you can't mention how you fit the job in the cover letter.
It might seem like a lot of work but you can probably have a "teaching" cover letter and a "research" cover letter for different job types, and then spend maybe 30 min per application customizing one paragraph for the specific position you're applying to. How do you customize? I mean really basic stuff such as saying how you could complete what is asked of you in the job ad (e.g. research with undergraduates, teaching the course(s) mentioned in the ad, etc.) If you want to get fancier by looking up the school for a little bit and then playing to their "shtick" (e.g. required senior theses) then even better.
For all I know you only need to do this for places that are somewhat teaching oriented. But it seems like a lot of people on here, even those who would prefer to work at R1s, are applying for teaching oriented positions since probably at least half or so of the positions fit that description. My opinion is not based solely off of the experience I'm having now, rather, this current experience is reminding me of advice I got from faculty at teaching-oriented places when I was on the market, and from my own experience as well as the experiences of my friends who saw better results with customization. I even had a friend who was forced into customization of one letter (given odd application requirements for that job that caused him to rewrite materials for that position) but who did not customize the others. He got his sole interview & job offer from that school. It made me wonder how many places wrote him off due to his generic materials sent elsewhere. Also, I just saw this today on vitae.com: https://chroniclevitae.com/news/1197-do-i-sound-pushy
I know we have been down on Karen Kelsky and rightfully so, but this was a very true piece.