How do I know whether I now have room for a project I once postponed?
Tyra Banks described putting an ice cream business plan aside while she took on another major project. Her example raises a capacity question that's separate from whether the idea is good. Before you pick up something you postponed, list what it would take from you now.
Include the work after launch: customer service, maintenance, staffing, and the decisions only you can make. Check the original plan's assumptions before you reuse any of them.
Then hold those needs up against what you've already committed to. Work out what would be delegated, delayed or stopped, and ask the people affected before you treat their time as free.
Pick a first stage that fits the capacity you can really support. A smaller scope can give you a useful test without bringing back the conditions that made you postpone the project.
Ask yourself whether you still want the role it would hand you. A good concept can come with an operating job you no longer want. Reviving a project is a choice you make today. You don't owe anything to an earlier version of yourself.