I still use the old style rubberised cotton airbed, they are still manufactured and they very rarely deflate. Most modern airbeds are made from plastic with a flock covering and they are very prone to leakage, both from the seams and from minute cracks that develop where they have been folded.
With regard to the size of bedrooms, many manufacturers state the number of berths based on sleeping bags without airbeds. Most people therefore buy a 3 or 4 berth tent to accommodate two people or a 6 berth tent to accommodate four people in order to ensure that there is room for the airbeds.
Our airbed never deflates, even after four years of use. It's a Royal rubberised one (the old style blue & red). It's also only four feet wide, so it could fit it into a two berth pod if we wanted to.
Another vote for the red and blue ones ..mine is 21!! (the same age as me ) and although I sometimes think about upgrading it to a self-inflating one there are no problems with it... the kids ones on the other hand were blue flock ones from tesco and they went this summer after 2 years and have been replaced by camp beds. Sarah x
We use Thermarest Base Camp self-inflating mattresses. Bit pricey, obviously not as thick as an air bed, but we find them much warmer and not at all uncomfortable despite not being "that" thick. Also, no bouncing...I've made a couple of figure of 8 straps that hold two together to make a double.
I use my parents old rubberised air bed, I remember them using it when I was 4 (I am now 25) the air bed is still going strong. Barely ever goes down and it is very easy to go get a replacement bung if you left yours at home (which we did once!)
I used ours in our Phad X3 I would have just squeezed it into a X2 but without any room for anything else. Size is roughly 200cm x 130cm x 8cm they do tend to be a tad smaller than the flocked air beds (have to say we never had much luck with them). Also on the lus side they take less time to inflate!
On a side note I don't know if you have read any of the other threads on here referring to being cold or condensation problems with air beds if you haven't you won't have seen that most of use who camp using air beds usually have one or two layers below (usually foam mats, picnic rugs, blankets) and some of us (depending on weather we sleep in a bag/how cold we get) have another layer on top of the air bed (underneath us) (usually a opened single sleeping bag or fleece) Worth investing (or searching out in loft etc) in as well as the bed.