QUOTE (Ascalaphus @ Jan 5 2011, 09:09 AM)

I think it'd be nice if both Substance and Foci abuse rules had been fleshed out a bit more. As a player, I hesitate to use drugs without knowing how risky they are - and therefore part of the game design isn't actually used.
QUOTE (TheOOB @ Jan 6 2011, 01:54 AM)

I think the important thing is to not punish the character for using foci, only abusing them. Magicians use foci all the time, and the majority have no addiction. The Force >= 2xMagic is a good rule, but tests should also be called when a character keeps a foci active for an extended period, many hours at a time, especially when it is not needed(for example the mage keeping increased reflexes on 24/7.
These two posts demonstrate my mixed views of addiction within Shadowrun. On one hand we've got a potentially scary reason that ties into roleplaying as to why to avoid drugs. This can take some of the element of metagaming out. Yet on the other hand, I too have had to have discussions with players about where foci addiction comes into play. So far though, we've not had to put any rules into place and we seem to be doing fine.
Now, if I did have to come up with a rule for foci addiction and tests I would agree with (Total Foci Force)>= 2xMagic. I can tell you that I would never allow players to simply buy hits for this test though. However, to the other point of extended foci duration, there are two parts to that I think you'd need to spell out. The first is how long of a duration is dangerous. The second is how long of a downtime do you need before you can do it again.
I have an easier time coming up with a simple for the maximum length a specific foci can be used before there is a risk of addiction:
(Force of that specific Foci) x (Magic Attribute) in hours.
Using the Increased Reflexes example, most mages will have a rating 3 or 4 sustaining foci for it. Considering a magic of 5 or 6 you wind up basically having to recast the spell somewhere around once per day, and risk exposing yourself to that drain. Similarly, a powerful Power Foci, say rating 5 and magic 6, would mean that after 30 hours on consecutive use addiction starts to become a risk.
Of course, the concept of addiction is totally avoided if you just have a rule for how long you can use it without a break but you don't specify a break duration. Again, using the increased reflexes example, just making a character recast the spell once a day to deal with drain but avoid addiction would still leave a character with a foci they can become very attached to having on basically all the time.
Now, a simple formula for how long the break should be is something that I'm having a harder time with. Right now the best I've got is something like:
(Maximum Safe hours as figured above) - (Willpower Attribute) - (Magic Attribute) - (Unused Safe Hours) = downtime, with a minimum of (Force of Foci) hours.
Using the Power Foci example listed above, activated for 20 hours, it would look like this:
30 (Maximum Safe hours) - 5 (Willpower Attribute) - 6 (Magic Attribute) - 5 (Unused Safe Hours) = 14 hours downtime before risking addiction. Given the power of a rating 5 Power Focus, if I had to make hard rules for foci addiction, this doesn't seem too harsh.
Similarly, lets look at a Magic 5, Willpower 5 mage using a Force 4 sustaining foci for Increased reflexes over a few different periods:
20 Hours: 20 - 5 - 5 - 0 = 10 hours downtime.
16 Hours: 20 - 5 - 5 - 4 = 6 Hours downtime (or some sleep)
12 Hours: 20 - 5 - 5 - 8 = 2, but Foce of Foci is 4 so 4 Hours downtime.
24 Hours: 20 - 5 - 5 + 4 = 14 hours downtime.
36 Hours: 20 - 5 - 5 + 16 = 26 hours of downtime.
Here you can see that if you used these systems a character would run a serious risk if they left a foci on for too long because they'd have to make a check then, and if they needed the foci again fairly soon they'd again have to make a check. This can create a slippery slope that could represent addiction. Even if the threshold is lower as another poster mentioned, there are times when dice will abandon you, and eventually even Edge runs out.
These were just off the top of my head, as I said I've not had to create hard rules for this with my group. I'd love to see what others think.