Is it better to take a longer holiday?

So, here I am pondering the intricacies of our holiday to India. This morning, I was pretty pleased with what we had planned - that is, Toronto to Brussels - 4 days in Brussels then some time in Mumbai - a couple of days in Pune and then on the "real" part of our holiday. Delhi to see the capital, Agra (Taj Mahal) and into Rajasthan. We plan on staying in palaces, seeing forts and showing the world to baby M. Then back to Mumbai and backtrack to Brussels for a couple of nights and return 36 days later to Toronto.

But then I started to think, if we are going all the way there - why not spend one more week and go and see a little bit more of India. I mean, I really don't know when we will go back there. There's just so much to show baby M around the world.

Should we be taking the opportunity and seeing more?
Here is my thinking process:

For staying a week more:
1) We are already there - might as well spend a week seeing another area.

Against staying a week more:
1) We'd already be travelling for a month (16 days in hotels) - is it fair to put baby M through more hotel rooms?
2) It'll be summer in India and I don't like the heat. No idea how baby M will react to it as well.
3) Because of the heat, really the only places we can go are the Northern parts of India and the Himalayan region. Not a bad thing, because I love mountains. But we are going again to the Rockies in June - mind you, as a mountain lover I can tell you that no two mountains are the same - but still - it's essentially mountains. On the other hand, you can only go to the Himalayas for about 4 months a year and I have never really gone to India this late into the summer season before and likely will not go again at this time.
4) Trip for 1 week will cost the bank around $1800 additional. Which is pretty cheap when you compare it to the cheesy resorts Canadians pay to go to the Caribbean but still it's money.
5) The Travel Insurance with the credit card company that covers us only covers a period of 31 days - I have no idea how to upgrade that.

Hmm....