Effexor XR(venlafaxine) when taken for long duration like 10 years, it has to be tapered down over months rather than discontinuing abruptly. Even an use of more than 7 days warrants tapering of dose and stoppage. It s not that your brain would have forgotten how to prepare serotonin. Venlafaxine just inhibits the reuptake of serotonin and serotonin will be produced by your own brain even while you are on venlafaxine. Only thing is over years, your brain would have adjusted to the dynamics of having the drug. An abrupt stopping would cause severe symptoms called as withdrawal symptoms. So i would suggest a slow tapering of dose over months and look for any resurgence of symptoms. By taking this slow tapering approach, the body can adjust to the absence of drug over time. I suggest you to taper the dose and stop it under the guidance of your consultant. Hope this helps you. Thank you.