Rearranging furniture?!  

It would probably be ok, but there may be a chance of change in the heating/cooling. Another problem is that air would be blowing out from under the couch and that is sometimes uncomfortable to people who are sitting on it. I used to have a register sitting under my desk and during the summer my feet would freeze because the cold air would be blowing over them a lot. Just keep that in mind while you're moving the furniture.

Unfortunatly I am not sure about the register and if it could do any harm if you put anything above it, but I can answer your first question. I do rearrange furniture every once in a while. I estimate 1 or 2 times a year if I also take the smaller furniture chances into account. At the time being I am moving into my new appartment so I guess the furniture will stay put for a while now . It has taken quite some time and effort so I will want to enjoy it first before rearranging .

i would also like to rearrange the furnitures to give new appearance to the house.
i feels that everyone likes change so why not we change the appearance

Hi. I know it won't hurt the couch. I think it will still allow heat into the room. I have a big area rug over my register and, the room still stays warm. You might feel a little bit more toasty while sitting on your couch though.
If you have central air, I would rearrange your furniture again in the summer for energy efficiency reasons.

I change furniture once a month sometimes. We have a sectional sofa set so you really can't change it that much but I like to try different angles. What can I say? I like change. I can't get it in other ways so I change the furniture or the paint color!
I would agree with the other comment, who said that the underside of the sofa would be warm. But make sure it s not too warm! You don't want to chase away your guests because of a hot bum, lol.

haa pretty much never. but i remember when i was a little girl i was constantly rearranging the furniture in my bedroom.