I’m one of those people who was grandfathered in to AT&T’s unlimited smartphone data plans, and for a long time I was quietly determined not to let go of it. It was partly the principle of the thing. (“My mobile digital lifestyle shall know no bounds!”) It was also the vision of all those wireless devices, including many yet to be invented, that I’ll no doubt want to incorporate into my life in the years ahead. (“Someday I’m going to need 50GB a month!”)

Today, after doing the research, I officially gave up my status as a holdout and switched my family to one of AT&T’s newly launched Mobile Share plans. On average we’ve been only using about 1GB a month of data between our two smartphones. Unlimited data was complete overkill. Based on the 4GB/month Mobile Share plan, we’ll be saving around $34/month, or more than $400/year.

Not exactly on the level of refinancing the mortgage, but enough that it was difficult to ignore.

For me, the sweetener was the ability to use my phone as a hotspot for my computer at no extra charge. I’ve been paying about $25/month for data on a prepaid laptop stick with another carrier. That’s one reason I was comfortable going with the 4GB/month plan on AT&T, to give myself plenty of data to play with, although it would have been nice if there were a 2GB or 3GB option. (AT&T’s plans jump from 1GB to 4GB, then 6, 10, 15 and 20.)

AT&T’s new shared data plans launched last week. AT&T is following Verizon’s lead by moving away from limits for individual phones — shifting instead to a shared data pool that can be accessed by up to 10 devices. T-Mobile USA is taking a different approach by launching a new unlimited data plan.

I contemplated switching to Verizon, which tends to have better coverage in my neighborhood, but the cost of new phones, compatible with Verizon’s network, would have wiped out any savings.

This is not the right decision for everyone. It depends on how much data you use and how many devices you have. In my case, for example, my data usage is lighter than it once was because I’m no longer making a long daily commute on public transit. (I live relatively close to the office now.)

Check your billing history, use this online calculator from AT&T or this one from Verizon, and talk it through with a customer service rep.

Did I make the right decision? Ask me 3-5 years from now when I’m using gobs of data for all those yet-to-be invented devices. In the meantime, I’m happy to pocket that $400/year in savings.

Have you gone through a similar exercise? If so, where did you end up?

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