I did an MR in June where I went:
SFO-DFW-FLL-DFW-SFO in one day, upgraded to F on all 4 segments.
AA520(757) 6:00-11:35 the usual F bkfst choices
AA1494(MD) 12:45-16:45 the usual F lunch
AA509(MD) 17:20-19:25 typical F dinner
AA1575(757)21:20-20:50 snack
3 of these were inside of typical meal times, wouldn't you say (DMT or not ;-) but the last segment was a bit late for dinner in the USA, so a snack was served... makes sense to me.