I don't have a layout at home. 
I run my trains at my train club. 
I've been a member for over 25 years. The club layout gets an update every year. Sometimes it's just a minor update, a new feature or accessory. Other times, it's more involves. Last year we started a modification to our main line track plan that shut down the mainline for 8 or 9 months. The mainline is running again but there is still some staging trackwork, switch motor installation and scenery to complete.
The big event on our calendar is our Holiday Open House. This is a major event in that it is the time when we give back to the people that keep us running. The layout must be up and running by December, although, it's ok to have some areas under construction. Our regulars often comment on the changes that took place since their last visit. Donations received during the open house make it possible to keep the layout fresh and operational for the following years.
Changing and updating the layout keeps it interesting for us as well as our visitors. It is important to keep working on the layout to keep the hobby and the club interesting. It is also important not to shut down the layout for repair for too long so the operators of the club stay interested. 
The projects planned for the next few years will not disable the mainline like last year. 
