According to NetDoctor, forever most likely, Jane.
Here is what they have to say :

   "Adenomatous polyps can all potentially become cancerous but the actual
risk per polyp is very small even if they are not removed. Some 50 per cent
of people aged 60 or over have one or more adenomatous polyps yet only 6 per
cent of people develop bowel cancer. As long as the whole polyp is removed,
there is no risk of recurrence or cancerous change of that polyp even when
cancerous cells have invaded the stalk of the polyp. Further polyps can
develop however. The risk of recurrence is greater if any of the initial
polyps was over 1cm diameter, if the original polyps were multiple (four or
more) or if any of the polyps show severe dysplastic (pre-cancerous) change
under the microscope. In these cases, colonoscopic surveillance is usually
recommended every five or six years."

You can read the entire article by following this link:

    http://www.netdoctor.co.uk/diseases/facts/colonpolyps.htm

As far as waiting for the 'scopes until he improves goes,
why not put it to your doctor ? We are all 'non-docs' here
so her opinion will be better than anything we can give.
She will also understand the urgency of the case.
Your husband sounds very poorly and it seems to be bearing on you too.
If he has no appetite and is steadily losing weight, you could ask you
doctor for a referral to a nutrionist or dietician if she will not see to it
herself.
Unless of course seeing to it herself is is exactly what she is now doing.

The endoscope is a long tube of glassfibres and is inserted into orifices
of the body  to conduct noninvasive examinations.It has a lens at the end
for focus and light can be sent down for illumination.Air can also
be blown down to inflate and make inspection easy, and also
forceps to remove samples.It is a wondeful advance in non-invasive
surgery and more of an uncomfortable experience than a painful one.
The surgeon tries to get the tube with a camera into your
stomach but the reflex peristaltic action of the gullet make you
regurgitate.

Once it's in the stomach you are more or less comfortable,and the surgeon
can see if there is anything there.
You don't choke.Withdrawal after the examination is a doddle. Maybe
it will bring his appetite back because he will have to fast.
The endoscope is also used to examine the gullet.

Perhaps something will be discovered which has nothing to do with
polyps, but whatever the outcome your doctor has taken a solemn oath
to care and try to help all patients including your husband.
None of us have.
I hope your husband will soon be fit and well again.

Old Bill