I start my carb motor and let it "warm up" for 20 seconds at around 2,000-2,500 rpms and its good to go..a bit choppy idle at first but strong and doesn't stall even in gear backing out of a turn around garage with tight space around.
Even with F.I. you should change the oil more than once a year.
Stock ignitions with these newer plugs can go years without changing plugs--my MSD 7 seems to "eat" the plug metal so I replace once a year..and all plugs are nice and clean.
I can't say carbs get better mpg but I have hear its not always that big of a difference, heck the new Viper is a gas hog and has F.I.
Some guys claim carbs make more peak power.
Too me F.I. isn't worth the cost to switch over to even try it, I'm keeping my old school dual carters that run pretty darn good in all type of weather from cold to hot weather with just a quick change of metering rods--secondaries jets seem to work fine year round without changing...unlike my Holley / Demon carbs in the past.