I'm still working my way up the pilot ladder, so I may be in above my head here, so excuse me for saying that I agree that it is important to look professional. I understand that you're not going to look your very best after that 7th leg, but please, don't just throw your arms up in despair; try and represent the profession well.
Here's something to think about- People always say that foreign airlines always treat pilots with a lot more respect than US airlines. I can say that it's pretty hard for me to spot a poorly dressed foreign crew. That goes for long and short haul- Virgin, Air Jamaica, Alitalia, Mexicana, TAP, Caribbean Airlines, Emirates...