I was walking with a friend today and lamenting the fact that my husband decided yesterday was the perfect day to sort through our many cans of paint. Yesterday, it was close to 100 degrees in the garage!
I bring this up because part of the reason we have so many different cans of paint--besides the fact that I am a serial room-color-changer--is because as a Realtor® I am often the last resort for sellers who need to get the paints out of their garage. Most movers won't take paint cans, they can't be thrown away (without drying them out first) and many buyers don't want to inherit them.
If you are many years from selling, I recommend staying 'on top' of your paints. As you change a color, dry out, or pass on the old color. Additionally, mark your cans well with a paint name (not just a number), the room it was used in and a date. This will make it much easier to keep track of what needs to be discarded and what is needed for a quick touch-up.
If you have already listed your house and have not yet dealt with the paint cans stacked in the garage or storage area, be sure to ask the buyer immediately what they would like you to do with them. Keep in mind, buyers are notoriously fickle; the best option is to get it in writing, or be aware that you may have to get rid of the paints at the last minute.
Two other items that fall in to this category (the deal with it early and often category) are wood piles and propane tanks. Be sure to ask the buyer if they want them, and if they don't, leave yourself plenty of time for proper disposal.
Believe me, my option of last resort is to take these paints in to my home--especially after the fun we had yesterday!