When my oldest son went to college out-of-state I purchased the extra long mattress pad and sheets.
I still have the mattress pad and I use it to cover an air mattress when my granddaughter comes to visit. I found the extra length allows the elastic to rest in the seam on the sides of the air mattress.
College is in full swing now, and you may be able to find the extra long bedding at a deep discount.
You will be glad you picked it up when you use it camping next summer. You cannot feel the vinyl when you use the mattress pad like you do when you are only using a sheet.