Oh, I don't ever take ratty stuff either, it's usually just things I don't wear anymore. The undergarments or socks are usually the ones that elasctic is streatched, have a hole on one side where my toe rubs or has been washed with something red (undergarments, not the socks). As long as they're clean and comfortable who is ever going to see them.
I usually go through my closet before a trip and pull out clothes that I never seem to wear, the things I wonder really why I ever bought in the first place or like you said, some older t-shirts that need to be replaced with new ones from that exotic port I'll be visiting.
When I travel somewhere other than cruises, especially if I have a washer and dryer, like a house or condo; I wash up the best stuff (never underwear or socks and drop them off by a thrift store. Some of the things I donate have only been worn once so that way I also feel like I'm giving something back when I travel.
Needless to say it does give more room for all the souvenirs without buying another needless tote bag or suitcase just to get home!
Think about it...new clean stuff when you get home instead of laundry?
You're gonna buy those t-shirts, fresh new socks and underwear anyway!
Have a safe and wonderful trip, where ever you go.