Well if you guys really want, I can adjust it.
How about this the addiction to alchemy is based on how much you have used it. For example if you used a lot of alchemy naturally you addiction will be greater, hence the heavy withdrawl symptoms will start after a month.
However say you didn't use much alchemy from the very start, this way you will have a stronger immunity to the addiction. As such you could last months on end with some head aches and migraines. What say? This way you could abstain from hallucinations for at least 5 to 6 months.