Hi Teri, I have a couple of thoughts...
you could create a project status of "Ongoing" to use for these perpetual Landing projects
whether you use Ongoing or In Progress as the project status, you can change the condition mode to "Manual" and then set it to "On Track" so it isn't showing up negatively on project health reports, etc
What are you looking to accomplish with the schedule from start vs. end date? Im thinking it makes sense to schedule from the Start Date. Our implementation consultant said that scheduling from completion can have other wonky impacts so that is in the back of my mind (haven't validated, we rarely, if ever, use this setting), but also wondering what benefit the schedule from completion date would have. Once a task is moved into an iteration, the dates are set by the iteration so I am assuming the same is true for issues? Traditional calculated project dates really get thrown off when planning via iterations.
Alternatively, you could add one Task on the project that is just the "master" task from the project start date to your projected end - set the start date and the planned hours that get you to today+15 years. This will help reflect that the project is open in perpetuity.
Another alternative could be to open a new project each fiscal year. Not sure if this would just create more work for you to update the routing rules, and reporting, etc. It would give you a specific point in time to re-review the items on the issues list (the backlog essentially) and clear out anything that is no longer relevant, copy anything forward that you do want to keep, and keep the overall project list to a manageable number of items vs growing it to hundreds or thousands over time?
We dont have the exact use case you are describing for intake of our agile work so Im not sure how applicable these ideas are. Id be happy to brainstorm more if you want! -Erin ERIN REED National Heritage Academies, Inc.