Is having just lower molar workable?

I lost Molar 31 20 or so years ago in an accident.

I have a bridge connecting 30 and 32.  It was put in following the
accident.

Approximately five years ago the bridge came out.  A dentist put it
back and said there was no guarantee that it would stay.  He said I
should replace it eventually.

Since then, it has come out at least once.  During cleaning, it popped
out, and the dentist put it back in.  He described the attachment as
"temporary."

I went to get the bridge replaced.

After making the impression, the dentist, actually two of them, told
me that they did not think I had enough attachable tooth area on 32 to
support a bridge, that that was probably why the bridge came off in
the first place, and that if I got a new bridge, it would inevitably,
they thought, come off again, sooner or later.

They showed me the impression, and I didn't doubt them.

After making the impression, they put the bridge back in.

They said they didn't think oral surgery on 32 would fix the problem.

The options are:

1.  Do nothing.  Leave the bridge as is.  Wait for it to come out
again, and then figure out what to do.

That would mean that I would have to worry from now on that it might
come out at any time.

It also might come out at an inopportune time.

2.  Replace the bridge regardless of their advice, and hope it doesn't
come out.

That goes against my instinct to follow people's advice.

3.  Implant.

That has two problems. 1) money and 2) for the next 18 months I am not
going to be in one place where I could get it done.

4.  Remove the bridge, and

     a) live without 31.

I thought when I got the bridge, I needed it because I could not get
by with a gap in there.  Is that correct?

     b) remove 32 and live without 31 and 32.

Is that doable, to live with just one molar, 30?

Does anyone have any other ideas?

Also, what did people do in this situation before implants came along?