What would be considered a good time to submit a WO application?

The WO train keeps moving. The longer you wait to jump on it the further back your kicking the can down the road.

They say that your career starts once you pin on the dot. Meaning that it doesn’t matter if you’re an E-5 with six years or an E-8 with 17 years in. When you ascend, you are all WO1s.

Submit a packet as soon as you are ready mentally if your going for technical field. I was 8 1/2 years and an E7 when I dropped mine. It isn't so much timing as qualifications. Have good ER's and PT scores.

I submitted my packet at about 7 1/2 years TIS. It all depends on your experiences garnered. Speak with your WO in your Unit or start the packet and have a few look it over. They will be more than happy to advise you.