Ron:
I had my Lycoming in the box for four years. On the advice of Lycoming, I never touched it and left it in the box. Once mounted and ready, it started on the second crank and has run perfectly since. You'll want to be aware of two things:
1. Do not take it out of the bag until you're ready to install and do not rotate the engine. Some people think they need to turn the engine every now and then to let the preservative oil re-coat the parts. According to my conversation with Lycoming, they recommend just leave it as it was shipped (sealed and stationary) until you're ready to install it.
2. Warranty. The Lycoming warranty is two years. The clock will start sometime after Van ships it to you (I seem to recall it's a year after receipt or first engine run whichever occurs first). In my case I didn't run the engine until after I had it four years. Once I ran the engine, I immediately noticed an oil leak which was traced to an improperly manufactured oil filter adapter on the engine case. Lycoming denied my warranty claim saying the engine was out of warranty. So read your warranty papers for their current conditions. If you let the engine sit for several years, it will probably be out of warranty. Too bad, because otherwise the engine has been great but my opinion of Lycoming is less so.
Chris