T-Mobile: Q4 strong, but can Un-carrier mojo last forever?

T-Mobile delivered another strong quarter as it continued to gobble up customers, but the outlook may indicate that its Un-carrier momentum can't last forever.

For 2018, T-Mobile projected postpaid net customer additions of 2 million to 3 million. That tally is lower than the 3.6 million net postpaid additions in 2017.

T-Mobile, which had previously indicated its results would be better-than-expected, reported net income of $2.7 billion, or $3.11 a share, on revenue of $10.8 billion, up 5.1 percent from a year ago. The earnings results got a $2.2 billion boost from the Tax Cuts and Jobs Act.

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For 2017, T-Mobile reported net income of $4.5 billion on revenue of $40.6 billion.

On the subscriber front, T-Mobile added 1.9 million net customer additions in the fourth quarter and 5.7 million for the year. Churn for postpaid phones came in at 1.18 percent in the fourth quarter.

T-Mobile touted its Un-carrier approach and its impact on the industry over the last five years. Indeed, T-Mobile has added more than 39 million customers over the last five years and changed the economics for rivals Verizon and AT&T.

What's unclear is whether T-Mobile can keep that momentum going as AT&T and Verizon have their own unlimited plans. T-Mobile's move to add Netflix subscriptions to its plans may be an indicator that it's running low on ideas. T-Mobile could continue to turn its Un-carrier approach into more of an Amazon Prime-ish buffet of benefits, but that'll get expensive over time.