Sunday 5/9 four hour run

Today's scheduled run was for four hours, 5 minutes running, 2 walking, and 1 slow jogging. It was a beautiful day, sunny and clear with little to no wind. I went back to Deephaven to the regular spot.
Before I get to the splits, I'll describe today's approach. I really wanted to avoid looking at my pace during the running portions. Back to what Bill and I talked about, it's more a perceived effort than a particular pace - although we have target pace levels. For a four hour run, I wanted to find a pace that I could maintain that long and feel ok at the end.
After a few hours of that, my legs started to get extremely tired and tight. It became difficult to start running after a couple minutes of walking. Actually, the most difficult/painful moments of the run were the first couple of seconds after running, and the first couple of steps while beginning the running portions.
Turns out I slowed down fairly dramatically after about 3 hours. The fatigue was almost completely in my leg muscles. I did not have labored breathing at any point today. Mentally I felt fine too. My legs just didn't want to maintain the pace for 4 hours.
I was happy to complete the four hour workout after cutting the last two runs a bit short for various reasons.
I never felt like I hit "the wall" today. Yes, I slowed down considerably but never felt like I completely crashed. I'm thinking I may need to slow things down on the front end so I can maintain consistency on the back end of these long runs. The 1 minute of jogging also added a lot of running time to the workout. Perhaps that contributed to the fatigue as well. Looking forward to talking to Bill about this.
My mindset in the last hour was not to nail the pace, but keep my best effort going despite my extremely tight quads. I think my feet were swelling up pretty good too because my shoes felt tighter at the run went on. I adjusted the laces and things felt much better :)
Here are the splits:
1 - 7:22 / mile
2 - 7:27
3 - 7:28
4 - 7:23
5 - 7:28
6 - 7:27
7 - 7:24
8 - 7:33
*extended break at car* (3:56)
Hour 2-
9 - 7:34
10 - 7:27
11 - 7:36
12 - 7:44
13 - 7:22
14 - 7:21
15 - 7:34
16 - 7:41
*extended break at car* (4:53)
Hour 3-
17 - 7:50
18 - 7:58
19 - 7:57
20 - 7:57
21 - 8:20
22 - 8:26
23 - 8:47
24 - 9:04
*extended break at car* (6:30) - legs were killing me, actually started "hour 4" at about 3 hr 19 min mark
25 - 9:46
26 - 9:47
27 - 10:25
28 - 11:39
29 - 11:37
30 - 10:42

Total: 23.67 miles, 4:06:32 (includes all breaks), average pace 10:25/mile, calories 3377