Someone here recommended it and I can't find the post now.
I tried it this morning. Around 6 I usually take 75mcg t4 and half my daily 25mcg dose of t3 but today I just took the whole pill. I did feel like my heart was a little fast at first but I think I sometimes get that even on a split dose. It wasn't crazy, but when I was trying to get back to sleep it seemed to be faster than a usual 6am resting heartbeat when you're half asleep. I didn't take my pulse but I might try doing that some morning when I'm more awake.
Two good things to come out of this experiment are 1) I didn't have to remember to take my afternoon dose, which I often forget until I'm running out of steam and 2) I didn't run out of steam. I felt pretty okay energy-wise all day with no real dips (until now, and it's bedtime so that's okay).
Good result. I'd recommend trying it if like me you have trouble remembering multiple doses or if you have dips in energy throughout the day.
And thanks to whoever suggested it.