I did a search and couldn't find this. I would think that this is well known but I really don't know.
Here's the situation, your stealthed and moving in on an opponent. But wait! Your Crippling poison (or any other poison) duration is down to 30 seconds! Don't risk unstealthing and applying new poison, be smart and prepare long before hand.
Step One:
Apply poison and Log Out
(I waited a bit and started the time at 39 for proof, but you can start at any time.)

Step Two:
Use up your time with poison, but not completely.
Step Three:
Un-equip your poisoned weapons.
(Screenshot not necessary, but i posted it anyways.)
Step Four:
Re-equip your weapons.
Again the steps go as:
#1 - Apply poison and log out.
#2 - Enjoy poison.
#3 - Before poison duration is used up, UN-equip the weapons.
#4 - Re-equip and enjoy restored poison, without breaking stealth.
Added Notes:
-This is a guide for those who don't already know about this.
-Also the version of the server is in the first SS.
-I have used this on other servers, although I never checked those versions , so test it out and post if it worked and with what version or pack.