>Is this true?
Yes, it is. More and more cells will mutate sooner or later until they
dominate the batch.
[color=blue]
>On average, how many times might I expect to be able to clone a yeast
>colony before it is significantly different from the original strain?[/color]
AFAIK, starting with fresh and pure cultures, it will begin with the 4th or
5th generation. As the yeast in bottles is already very stressed, the risk
of already defect or mutated cells to take over the batch is IMO higher.
[color=blue]
>* What is the nature of the mutations? i.e., What sort of flavor changes or
>other behavior might I expect? Don't wanna brew no skunky beer :)[/color]
The changes often result in faster und higher attenuations, but with more
esters and/or off flavors.
[color=blue]
>* How do the yeast labs (Wyeast, White Labs, etc.) perpetuate their yeast
>strains without the same thing happening to them?[/color]
They regularly select the strains and seperate mutation from original cell
by cell. Microscopes and sometimes trials help them.
[color=blue]
>* Finally: Maybe mutations aren't always a bad thing. Has any of our group
>deliberately mutated a yeast strain so as to "encourage" mutation in a
>certain direction?[/color]
Not yet, but of course this is right; many wanted and selected strains are
nothing but mutations from other strains...

--
* [url]www.brauherr.de[/url]
* (wenn Bier für Sie nicht nur gelb ist und blau macht)

** Wer das bayerische "Reinheitsgebot" für eine deutsche Segnung hält,
** der sollte auch Michael Glos als Bundeskanzler wählen.

***None of those is translatable without loss.
***I regret, you shouldn't.