At what point do you say goodbye to naps?

I know I am not ready for the little kids not to nap, but some days I wonder is it worth the many trips up and down the stairs??
The other day I made the mistake of trying to have Duncan lay down upstairs with them. Well instead of napping, they made a slide out of the mattress'.  I should of known better than to have Duncan lay down upstairs. Now they rearrange the mattress's every day at nap time. And almost everyday make a slide. Today they have been upstairs for 2 hours, no one is asleep. I have taken one mattress out because they took the sheets off, went back up to change a stinky diaper, and they had just moved down the line and more sheets were off! Hopefully they will go to sleep soon, although I am not holding my breath.
The other day I went to check on them because they were laughing and caring on, Elliott and Olivia had no clothes on, but when I had to go back up awhile later, they were both naked. Now everyone wears pj's backwards. I am sure soon they will figure out how to unzip each other. I don't put anything past my kids.
Until we figure some other sleeping arrangements out, I guess we will just go with it and what ever happens, happens! They generally do well at night, just naps are hard! God doesn't give you more than you can handle. I remind myself of that often!
I looked online to see how much a 2 year old "should" sleep every day. Well 13 to 14 hours, our kids sleep 12 or 13 hours at night. Maybe they don't need a long nap. They will have "rest" time, which is not really "restful" because they run around and play!