This one takes me back a bit. It is really part of the infinite variety of instruction, and a reason why it keeps people's interest. I relate to a lot of what has gone before.
I used to worry about two aspects, which I think are different:
- the students' poling ability
- their mental attitude, decision-making
One immediate problem is that it is difficult to influence the latter. You can show a good example, which is obviously key. Make sure you emphasise weather checks, paperwork, W&B pre-flight planning etc. - not just telling them to do it but being seen to be doing it yourself. But the students bring their life attitude to flying. I believe in the USA they call it the doctor syndrome or similar. If past experience is of taking risks to make things happen, they will tend to do the same with flying. It is probably worse if the student is older and has more expereince. Just think of one or two F1 racing drivers who were pilots over the years.
Within the civil PPL world there is much more flex than, as I understand it, there is in the military. So if Bloggs is able to pay more than the minimum it can be OK to let them go on. However, you should keep him/her updated on your views on their (lack of) progress. As Whirly suggests, you need to review why progress is poor, including them in the discussion too.
A lot of people with the money to learn to fly heles are busy. They may be in the habit of burning the candle, and it is worth talking about that. Get them to turn up half an hour early and chill out in the airport cafe.
Don't be shy about considering whether there is a mismatch between instructor and student. I never like lots of changes in instructor but one or two, especially for progress checks and standardisation reasons are justified and useful. The other instructor may have some ideas that work for the "problem" student.
I recall a number of students who went on for much longer than normal who finally became good, safe pilots and aware of their limitations. I think they got enormous satisfaction from mastering something that was (for them) very difficult.
I also recall a couple that I "gave up on" - that is not the right expression. I sat them down finally and suggested that maybe flying was not for them. Some thought about it, took my advice, and as far as I know are now happily digging up lumps of grass on a golf course somewhere. I do recall one who left the school I was at, and went to a local cowboy outfit. I passed on my thoughts informally with the training notes. He got his PPL(H) and whlst doing a bit of SFH piled the R22 into an off airfield confined area. He wasn't injured. The R22 was hired from the cowboys. He then gave uo flying. So not a bad result in the end, but a worry. What more can you do though, about such cases?