After promotion to SSG and completion of SSD3, when would you recommend a soldier submit a 4187 to attend SLC?

Its great your thinking about this but you can not attendt SLC until yoy have been selected for SFC promotion this all part of the Armys S.T.E.P program this has been around for a while now!

If you are trying to get promoted with your peers wait until they tell you to go. If you want to pass your peers. Prepare the 4187 and submit it. Go immediately. Its a school.
You only have to ask yourself what you want out of the Army, no one elses career path matters when it comes to yours.
Take care of your Soldiers and take care of yourself. If you do that the mission will be successful and so will you!

I'm in the guard and all I had to do was complete ALC, then SSD3, and ask for available school slots. Since we Now have the select train educate then promote (STEP)system you want to make yourself eligible for E7 once the board comes around… if you're eligible and you don't have slc you end up taking the promotion and working in an E7 slot until you graduate SLC,then you get pinned. In turn that could be a lot of money you're gonna lose out on. So I would suggest go the leadership school as soon as all prerequisites are met and slots are available.