Some help. GH3 and OMD together. Is this silly ?

I can't really offer you any advice other than to say that 2-3 years is not a long time IMHO. I'm still using a Pentax K100DS that's almost 5 years old and a Canon A650 that's almost 6 years old, and both of them still work perfectly and take pictures that were just as good as the day they were new.

It's not until just recently that an M43 model has finally appeared with 1080p60 video, which is the technology I've been waiting for - so I'll likely upgrade soon. I expect my next camera to last for at least 5 years (but I'm hoping that I can drag it out to 10 :-)).

IMHO you're wise to take the long view and spend time thinking about what will work best for you.