Brad Hudson likes to talk about a variety of tempo paces. I don't have his book in front of me, but I believe he generally uses 3 different paces to distinguish different tempos, but he also acknowledges they can bleed together. He does use the classic Daniels one hour race pace, then a slightly slower 1.5 hour race pace, and then a 2.5+ hour race pace. So workouts for each of those might be 20-30 minutes, 45-60 minutes, 60+ minutes. He also assigns progression tempos that would start with 10 minutes of the slower tempo, recover 2 mins, 10 minutes of the medium tempo, recover 2, then 10 minutes of the classic tempo, or something along those lines.
And I think some of the older coaches, like Lydiard, would talk about the slower tempos being just as effective as the shorter ones, you just need to run much longer to get the same benefit. I feel like I became very aware of the Daniels one hour tempo from things like Runner's World when getting the most bang for your buck was always in one of their headlines.
My favorite longer tempo to do is 60 minutes at an HR +/- 3 or so beats of my marathon HR. Depending on the day or week, this gives me a pace that is +/- about 15 seconds of MP. Sometimes these end up being slightly progressive in that it takes me a little while to settle into feeling comfortable at that HR, so the latter miles end up being quicker. These sessions give me a feeling of staying in close touch with longer race fitness, and they also leave me feeling surprisingly good. During a buildup to a marathon or half I'll end up doing 2-3 a month, and the paces tend to drop over a few months. I should say that early in the season I will often start with around 40ish minutes and built to 60-70 minutes.