I would passionately urge against locking discussions merely because some length of time has passed. Some plant things happen very slowly and 2 years is not enough time to determine that no new posts will be added to a discussion. That would severely diminish the value of this site to me. I use various discussion to track plants over very long amounts of time. This isn't FB where discussions are "here today, gone tomorrow." That is one of the primary reasons I haven't used FB for 4 years. It would be personally devastating to invest years in an experiment and then not be able to come back to share and discuss the results.
Frank, which forum is moving so fast that you're having this trouble? Why is it difficult to just not click into discussions that do not interest you?