As noted by several others here, the times for most techniques are guides only
to provide a range. The results depend on many  factors such as different
fixation and processing techniques and times, thickness of section, type of
tissue and final result that is desired.
I would suggest that if you get 10 histologists together in a room (always a a
dangerous thing to do) you will get 10 different opinions as to what is a good
hematoxylin and eosin. This is because we all have specific biases and while the
overall accepted general picture may be the same there are many subtleties. For
example for photography we often will have a deeper eosin so that the final
photograph will be better. When staining for nuclear detail there may be
differences required between staining for bone marrow compared to staining a
section of the intestinal mucosa.
The best advice I would give to  give beginners is
1.     start with the published technique and then to experiment with various
times and concentrations, varying only one parameter at a time.
2.    understand the general principle behind the technique that you are using.
Not only will this make you technically better but it will allow you to
determine at what stage an error might occur ....and it  is also a lot of fun.
I trained learning the principles behind the stain I was going to use well
before I actually carried out the staining.
We were taught that there are technicians and technologists.
Technicians can follow a procedure to its conclusion but may not necessarily
understand the mechanism behind it.
Technologists understand the techniques they are using and are therefore more
suited to correct errors should they arise.
I would always choose to be a technologist rather than a technician.
Unfortunately the employer does not always recognize the difference. Section
cutting and staining may appear to be easy to the uninitiated. I'm sure that
most of us have suffered from the graduate student who will be seated and will
be able to cut some great sections from the block we have selected. Their
attitude changes dramatically if we present them with a "difficult" block or if
a problem occurs during staining.
Unfortunately  the tendency is to employ several individuals with limited
training to one with extensive training because of "cost effectiveness".
I notice that along the lines of RIF that several institutes have tended to
place MLTs in charge of histology laboratories. This is fine if they have
received appropriate training in at least the basics of histology. Unfortunately
some have not and this then becomes unfair both to them and to the individuals
they are supervising.
Barry

"Gary W. Gill" wrote:

> Histo is also a dyeing art.  Such predictions may or may not come to pass.
> It's difficult to supplant widely used methodologies that have existing
> infrastructures.  Histo and cytopathology continue to flourish because they
> provide such a wide range of useful information from microscopic
> examinations, however imperfect and limited they may be at times.  Ask the
> former employees of Neuromedical Systems, now bankrupt, who invested perhaps
> 7 years and tens of millions of dollars trying to get PapNet accepted how
> difficult it is.
>
> Gary W. Gill
>
> snip>>>
>
> My course co-ordinator always claimed
> histo was a dying art because in the future there will be no need to excise
> lumps of flesh from people because illness will be detected & treated by
> the new emerging technologies.
>
> R. Wadley, B.App.Sc. M.L.S, Grad.Dip.Sc.MM
> Laboratory Manager