I think it depends on your health. If you are prone to arthritis or have bad knees, I wouldn't do it. If you have arthritis in your family, I also wouldn't do it. I had great knees until I had twins in our 3 story home. It's not just cups of tea that you have to think about, but also laundry, and if you have babies, nappies and rubbish.
Our lounge was on the first floor and every time you have a treat, a packet of crisps, candy or whatever, you need to carry that wrapper downstairs. Every time you want a cup of tea, you go downstairs, you forget your biscuit, you go back downstairs etc etc. You carry dirty clothes down 3 flights, then you need to take it back up 3 flights. Eventually your knee starts cracking or your landing becomes a dumping ground for things that need to go up or down.
It also gets very hot, but i suppose this depends on where you are. We had a ceiling fan in every room and we had to use them a lot. Our house was semi detached so that probably contributed to it.
On the positive, you will have so much space. You will have an extra lounge space so you can have different rooms to watch tv if you don't agree. You can store all that extra stuff, and the rooms are larger.
I would do it, if the main lounge I was using is on the same floor as the kitchen, otherwise I wouldn't.