Thank you in advance…

I’m taking a lot of time with this project and it will be months and maybe a year before I’m ready to spray color and finish the truck.

What stage would you leave the truck in?

My stages are the following…

Epoxy primer
Body work (almost none - replaced or put new steel on it)
Skim coat (maybe as it’s really straight now)
2k high build primer

Assume stop before the next stages…
Sealer
Base
Clear

Really in my mind I leave it in epoxy or I take it all the way to high build and perhaps don’t sand it for base yet?

The vehicle is completely frame off and in a climate controlled shop.

Thank you all again…

In a climate controlled shop, it's probably safe in either epoxy or hi-build. Personally, I would finish it all, even blocking the hi-build, and shoot a coat of epoxy on it for protection. Because even in a shop, things can be touched, get spilled on, etc. Epoxy offers the best protection.
When ready to paint, sand, reapply the sealer and go!

Agree.

Mix some epoxy primer 1:1:1 and spray a sealer coat over your finished sanded 2k primer. It can set like that for a very long time. When you are ready to paint, you will need to scuff the sealer coat and apply another coat of epoxy sealer, prior to shooting your base coat.