I've been using the dilution method for over a year, and the whole 48 hour window thing makes me REALLY uneasy.

I tend to take my drug test (Which are monthly, and I DO use dilution.), smoke for 7-10 days, and obstain for 15-20ish days. Using dilution after a little over 2+ weeks has ALWAYS worked for me. 11 Drug tests, 11 pass.

KEEP IN MIND, my probation officer doesn't care about dilute test, she just cares that there's nothing showing up positive, so I don't use the creatine / vitamin step.

Remember, dilution is great, but abstinence for a decent period of time will help you MUCH more than anything else. Dilution is a handy way to secure the passing of your drug test, permitting you followed the rules.