I think that this would be really useful and reduce the amount of redundant topics that are created in trade subforums. For example when i create a topic like this: http://forums.d2jsp.org/topic.php?t=74108334&f=226 or http://forums.d2jsp.org/topic.php?t=74108210&f=226 I need to be able to update my OP to reflect my current inventory and current prices as these constantly fluctuate depending on the market shifts and when I trade/sell items.

I propose that the OP of a trade thread is able to edit/update the post for atleast 20-30 days after creating it.

3 days is plenty.

http://forums.d2jsp.org/topic.php?t=71042066&f=28

I disagree. ^^

I agree with Rigzy here.
As long as you edit once within the three days you are good.
dont see a reason for longer.

Edit once every 3 days, doing so enables you to edit the op for an unlimited amount of time. Please see Rigzy's post for a link to the announcement of this change, further changes will not be happening.