Is it a good idea to reassemble the engine, or should it take place closer to completion of body work. It cold take 18 months to finish the paint work on my car

Is it a reconditioned motor? It looks quite clean. If so it probably has grease on the tappets to protect it and should be fine left alone. If not if you turn it over monthly it should be fine.
That's my opinion. I have a motor bench that allows me to run spare motors and takes 20 minutes to swap the motors around and lets me watch them run. No exhaust but headers are installed so neighbours don't like me much.

Up 2 now, have been using crc 808 silicone spray. All parts covered in gladwrap. My daughter continues to nag, things just seem to be moving not fast enough. I have found someone in the area willing after christmas, to assemble the engine. I'm in no rush to install the engine, body work may take up to nine months. Question being about crc 808 silicon spray, is it recommended ?