Archie, welcome aboard, glad I could help, and thanks for sticking with it. :-)
This topic comes up fairly frequently, and I should probably do a round of thread combining and then sticky the result. So if the following links all go to the same thread, that's what happened. :-)
A couple of starter threads:
Programmers / Developers / Creatives: What are your contexts?
Working in context mode
If it's any help, I know our CEO, Ken, uses a system similar to what you were thinking about to manage his various roles here. He's got a "Coding" context and a couple of "CEO" contexts related to the different kinds of headspace he needs to be in when working on stuff.
As far as rule-breaking... I don't know if there are any "rules". Useful guidelines, maybe. In general, I try to keep my contexts specific enough that they're useful, but general enough that they get used regularly. Not counting my various contexts for folks here at Omni, I have 18 that I use regularly.
When you're starting out, though, I'd say go ahead and add a new context if you think it would be useful - you can always prune ones that don't work out later on.