Should I give up my "grandfathered" unlimited data plan?

My service provider is currently offering much cheaper plans for talk/text and tiered data than what I am currently paying for my “grandfathered” unlimited data plan. I am aware that most service providers are desperately trying to push people out of their unlimited data plans, or throttle their data usage if they abuse the unlimited data. I do enjoy having an unlimited data plan, as it makes me feel like I can do whatever I want for as long as I want on my smartphone, and never worrying about financial consequences about how much data I use a month.

I share the unlimited data plan with my wife, and we use roughly 3–5GB of data a month together. We have been offered a couple of alternative plans at a much cheaper price, and could stand to save around $30—$45 a month depending which alternative plan we choose.

So, back to the original question; should I keep my “grandfathered” unlimited data plan? Why or why not?