cast iron grill/griddle... multi-tasker??

Found a Lodge, 2-burner, grill/griddle at a yard sale a while back... maybe $2-3.  Didn't NEED it... just WANTED it.  It sat in its "storage" area (between washer and drier) along with baking sheets, until a week or so ago.  Hadda pull them all out and noticed rust on bottom edge of CI.  Sure it's from lack of use and proximity to washer??  Clean-up was easy enough.  It has been living on top of my stove since then.  I KNOW one of the things about getting the best use out of CI s to USE IT... and often.  Well, I rarely need that kinda cooking area.  Then had a brainstorm!?!  Though I don't know for a fact, imagine that most flat-top cooking surfaces (diners, steak shops, etc) are just a slab of well used metal over a gas flame.
 
Since the grill/griddle has been on stove top, have cooked ON TOP of it in pots/pans a few times.  Today had some shrimp I wanted to boil up.  Just put pot with shrimp and hefty dose of Old Bay on top of griddle side and turned on gas.  Was thinking I might have some smoke issues... but none.  Wasn't fast... thinking CI acted like one of those "flame-tamer" trivet-y thingies.  Know I'd have to do something crazy to remotely damage this slab-o-iron.  Gonna alternate burners (rarely need all 4) and rotate/flip grill/griddle.