If you and your new spouse have been living together for a while you might consider the following.  Newlyweds, who often have new and attractive under garments, might not relate to these tips.

Pack old underwear when you travel.  Everyone has underwear that has elastic that is gone, or a hole or two.  Accumulate old underwear during the year and keep them in a separate drawer or box and save them for when you travel.  You can also pack old socks or old undershirts if you're going to a cooler climate. 

At the end of a day instead of putting your dirty underwear and socks into a laundry bag, throw them out!  If you're going to be gone for 2 weeks, that's a minimum of 14 pairs of underpants or 28 pairs for two of you, plus undershirts and socks.  That will be a lot of room in your luggage at the end of the trip.  More room for souvenirs!! 

But don't be surprised if housekeeping removes the clothes from the garbage can and places them on your bed.  This has happened to me several times in poorer countries where they would never throw out what looks to be perfectly good clothing.