Well.. the financial requisite is smaller with the marriage extension, but they do have to check somehow that it is not just a proforma marriage. Hence why they visit and all that. Its hard to be proforma over 50 years old ;)
In my case, we lived in a rented house before, but were planning to move to my wife's house in her family's village after the marriage. The immigration did not care about the rented house, even though we lived there by the time of application for the extension, they wanted to come visit in the village where we would live after, I had only been there on visits before.
We served them lunch there and they wanted to see the village headman. He had to sign some papers. They took some photos of us in front of the house. Took about one hour in all, with no problems. They were nice and friendly the whole time.
Was about to ask the same.. I am making my second one year extension based on marriage in october. I read somewhere that it was 2 months first time and then 3 months subsequent. So I made mine ready already in june.. But better too early than too late I guess ;) Nice to know for next time though!