I'm a charcoal man myself, but I acquiesce to my brother's grill on the weekends when he is buying
I think the new grill has efficiencies that will contain and concentrate heat in different ways than your old grill. The consumption rate overall might be higher, but the overall experience I think will be very much worth it. I have to admire the ease and the conveniece of my brother's propane grill over my old trusty rusty Weber grill (but never the taste -- NEVER!)
You seem to have a great thing going. In my experience, relish also the favors of a caring mother-in-law (something I have yet to experience).