I have mine side by side. The newest(mostly used for movies) centered and the old one is off center(tv watching). My pre pro has dual hdmi outs so i just toggle between the two. The only problem I have is... I didn't leave enough space to remove the bulb from the old projector which is used the most so... I have to take it down to replace it. Not really a big deal anyway. I tend to clean the inside and any dust accumulation at that point.
It's definitely nice having two projectors though. I've had a few hiccups with my old projector(bulb explode, odd hdmi issues) which made me switch to the new projector. Really comes in handy when you're hosting and it's your main TV. Nothings more awkward when you have guests come over for a hockey game and your projector isn't working Or the bulb poops on you. Not fun.