Growing up, I slept on a bunk bed, (both top & bottom), a waterbed, a single bed, a double bed and a futon.
When I was pregnant with my first, I was asking around for a second-hand crib and my co-worker said: Get a king-sized bed.
Up until then in my relatively short newlywed life, we had a queen bed.  It wasn’t ideal as my husband is over 6′ but you know how things seem much cozier in your 20’s! I refused to accept that I would have a baby sleeping in MY bed.  My child would definitely NOT sleep in my bed and would do as I said.  After all, who is the parent here?  (These were all my parenting philosophies pre-actual parenting).
When my eldest was 2 and I was pregnant we finally got our king-sized bed. It also quickly became too small with a baby, a 2 year old and of course the husband all jockeying for prime real estate on the bed.
Now here 10 years later, the boys have finally settled into their own beds and my daughter somehow ends up in our bed by morning about 80% of the time.  There’s also a small dog that sneaks in along with 4 or 5 stuffed favourites that follow the child into the bed. The child slowly turns sideways and I usually end up hanging off the side of the bed.  Sigh.
After a King sized bed, the only thing bigger would be an entirely padded room I guess?