I to am concerned about that, so my approach has been "final assembly" followed by a quick installation. I have heard "rumors" from various sources that it IS a good idea to install and start as soon as practical after assembly. In fact I think Comp Cams is one who also recommends it. Out of cam lube? "Torco MPZ" will work fine!
IF I was going to wait "sometime" before starting I would not bolt down tight the rocker assembly (no pressure on the valve train). You would also be able to pull each lifter and re-lube on the bottom of each shortly before "final assembly" and startup.
Storing it for awhile? A little Marvel Mystery
Oil in each cylinder couldn't hurt! Leaves a better "film" than engine
oil does and penetrates to every crack and crevice.
My engine build thread:
427 side oiler engine build "Blog"