I can only speak from personal experience.
I became a JW in 1971. When I had my "Bible study" the Elder who took it never mentioned 1975. We did the book "Freedom Everlasting in the Sons of God" were it mentioned that 6,000 yrs of mans extistence would end in 1975. But it was regarded as a side issue.
There never was a sense of urgency in the congregation as 1975 got closer. I think because our Elders didn't go in for speculation. Probably because they were mainly in their 60's and 70's. They kept a tight rein on it I think.
Amongst the congregation members there was a "maybe it is maybe not" feeling. There were a few weddings in 1974. Also none of those he did get married bought a house until after 1975. But thats about the closest it got. I mean I even had my first child in late 1975 and no one said a thing.
In fact after 1975 our congregation grew and had to split into two. Then in late 1980's we had to build a new Kingdom Hall as we were growing. Expecting even more growth. But then from 1995 onwards the congregation has not grown and many have left. Today I would say the congregation is about the same size as when I joined it in 1971.
But there again having spoken to others since I left the JW's. There were some who did take it seriously. One guy I met spoke about how his father sold his business bought a caravan and set off with his wife to preach in the West country, Devon Cornwall etc. Of course when it didn't happen his father was shattered and spent his last days living in a rented room above a shop.
I'm sure many other can give similar stories.
PS
After having read some of the above postings.
Nothing like that ever happened in my congregation. No one gave up work or moved to "where the need is greater" . We weren't told to offer Bible studies etc and get them done in six months.