We tend to glorify the startups too much. As Steve Blank says “a startup is a temporary organization designed to find a scalable business model”. What this actually means is that each day you spend in “startup mode” is a failed day. You still haven’t found the scalable business model!
You should celebrate the day when you’re no longer a startup. That means you’ve succeeded.
(Thanks to Gullfot for inspiration.)
Update: got some feedback on this elsewhere and I would like to point out that I personally love the startup phase. The problem is that the startup itself must leave this phase as soon as possible. This creates an interesting tension between the entrepreneur and the startup which is one of the reasons you as a startup entrepreneur should build a system, not a product.