Is Robe of the Spring still dropping?
 

If so, seriously take it off. It dropped a few times ever on live.

How long should it drop?

When I try googling it, the first mention is from 2006. Not really a lot of info on it...how do we know it's classic?

If it ever stopped dropping it would most likely be the VP revamp in 2004. Zero evidence that it was removed in this era. Or ever.