Some, even years later, still have pertinence, but true that most are not that way. One reason NOT to lock them is new subscribers come in often enough by replying to old threads and number of subscribers can have an effect on how much one can charge for advertising.
Just an opinion.
When a thread gets to one year old lock it.
I'm see threads that are 3/4/5 years old pop back to the top.
I doubt the original poster is still looking for an answer.
If someone is having the same problem let them start a new thread.