The days of truly unlimited LTE data on Verizon Wireless are coming to a close. Today, the largest US carrier announced that it will begin applying its "network optimization" practices, which previously only affected the 3G network, to unlimited 4G LTE customers starting October 1st. Beginning on that date, the carrier will slow you down if you're "connected to cell sites experiencing heavy demand." But Verizon's policy is far from straightforward, and it's in no way universal. To risk slower speeds, you must also meet all of the following criteria:

You're using a 4G LTE smartphone on an unlimited data plan.

Your current data usage falls within the top 5 percent of all Verizon users. This ceiling will almost certainly fluctuate in the future. As of March, hitting 4.7GB in a single month was enough to put you over it.

You're a month-to-month customer. Most people probably fall into this category, but if you've recently managed to renew your contract, you don't need to worry about throttling. This is one situation where being under contract is a good thing. Of course, extending an unlimited plan isn't supposed to be technically possible anymore. But where there's a will there's a way, and users have occasionally discovered loopholes that allow the plans to be renewed for another two years.

If you can check off all those boxes, you'll be subject to throttling and may experience video / music buffering, slower web browsing, and other interruptions that come along with reduced speeds. And it won't be for just one month: you'll potentially have to deal with throttling the following month, too. Again, this policy only applies in areas where the network is seeing heavy demand. You might be throttled in one town and experience regular, fast speeds in the next. See? We told you it wasn't straightforward.

And Verizon is pushing that point. Still, it's not like you have any control over what cell tower your phone is connecting to, so let's put it this way: if you're in midtown Manhattan or any other major city, expect throttling to be a very real possibility. Less so if you live out in the sticks somewhere. "The vast majority of data customers will not see any impact from Verizon Wireless’ Network Optimization policy, and will be able to browse the Internet, stream music and videos, upload pictures and send emails as they always have, " the carrier said today.

So Verizon seems confident that a majority of users won't notice problems. But if you're one of those crazy people using an unlimited Verizon data plan as a substitute for cable internet — yes those people exist, and Comcast loves them — it may be time to start researching alternatives. Anyone still holding onto unlimited data at this point is doing so for a reason. Starting in October, you'll need to again weigh whether it's worth the cost.