I have done:
OAK-DFW-BDL-DFW-OAK all in one day twice. At OAK, the GA's laughed when the boarding passes printed. At BDL the GA shook his head and thanked me for flying on AA
OAK-LAX-SAN-LAX-OAK all in a few hours. No questions, as it was during the Great Offer on UA so they were used to it.
SFO-LAS-DEN-ORD-MKE-ORD-DEN-LAX-SFO with an overnite stay, so the only one who questioned my sanity was my aunt in Chicago who feed me dinner that night.
SFO-PIT-PHL-CLT-FPO-CLT-DCA-PIT-SFO with an overnite stay at CLT. The only place any hassle at all was FPO when they questioned my about the nature of my trip as I was there only 1 1/2 hours. I assured them I would be staying next time, that this was a CMR. They laughed and sent me on my way. Though they did search my bag at the US Customs area in the FPO airport. I was glad that US Customs was cleared before we left as I had a very close connection at CLT-DCA.
SFO-ORD-MIA-CDG-XYD(Lyon)/LYS-FRA-CGN/QKL-FRA-QKL/CGN-MUC-LYS/XYD-CDG-MIA-SFO where I didn't sleep in a bed for about 48 hours, until I arrived at Cologne Hyatt after midnite. The second day was in Frankfurt so an easy day before returning to Lyon for another overnite stay. Spent a lot of time in airline lounges:
SFO AC just fair
ORD AC excellent Term3 Concourse H large club, looks new and very comfy. Also has a separate smoking room that doesn't impact the non-smoking areas
MIA AC in Concourse B (?) it is small and crowded with a tv and a bar. Use the one in Concourse E instead
CDG AA Arrivals Lounge is a little bit of a walk but good showers and comfy for a small lounge with coffee/espresson maker, drinks and snacks
LYS Mont Blanc Executive Center is tiny and the smoking area is not separated from the non smoking area in any appreciable way. But more comfy than the public areas which are crowded. Had drinks, coffee, snacks and newspapers
FRA SEN Lounge in the intra Euro terminal was fair, definitely not much more than drinks, coffee and snacks with a few comfy seats
CGN SEN Lounge is small but very comfortable seating. Drinks (seems all of the SEN Lounges have beer on tap,) snacks and papers
MUC SEN Lounge is one of the nicest lounges, large, lots of comfy seats, a "sleeping" area with three lounge chairs that almost go flat in a dimly light room, showers and great food selection
CDG AC is good, comfortable though feels a bit small as it is wrapped around the circle of the Terminal walk are. Just drinks, coffee and pastries though, with papers and tv
MIA AC Terminal E is a great lounge, large, a lot of computers, though 2 were broken, and good bar and meals are available