Oh yes. An extra one would be of negligible additional use in terms of putting guests up given the probability distribution of the number of guests visiting me at any given time, but keeping it clean would add to my housework load. I wouldn't say no to a few more cubic metres of junk-storage space in my existing spare bedroom, but a whole nother room would be excessive.

Hm. Maybe you feel you're already being profligate with your bedroom-havingness :)