In this Best Practices:
HP consultants recommend using Proposals for planning ongoing cross-year projects in annual period. I have several questions:
How is annual planning process organized in your case?
You can use different proposals, each of them may eventually become a project.
If all these projects have a common goal, you can combine those projects as Program.
PPM allows you to also link proposals with other proposals using a parent - child dependency.
However, at the end of the day, if a proposal passes all the approvals it will become a single project.