You should be getting feedback earlier than you think.
But what does that look like in practice? What do you focus on? How do you get the info you need?
Here's what has worked well for me:
Before writing any code:
- Drawing low-fidelity sketches
- Diagramming the flow of information
- Using a checklist
While writing the code:
- Time-boxing my work into 2-hour chunks
- Sharing my progress (at least twice a day)
- Asking "is this acceptable as is?"
It's never too early to ask for feedback. And if you wait until you absolutely need it, you've waited too long!