The finance chiefs of Verizon and AT&T cautioned it will take years for 5G to build into a substantial revenue stream, even as the operators moved forward with deployments of the technology.

Speaking at an investor conference, AT&T CFO John Stephens (pictured) said the operator doesn’t expect 5G to generate material revenue in 2019, adding the fledgling business is “going to take some time to evolve”.

“Will there be a lot [5G revenue] five years from now to where we sit down and say ‘Oh my gosh, how did we ever live without this?’ Yes, I actually believe that. Am I here today to represent to you that we have X dollars of 5G revenue in next year’s plan? No, I’m not.”

Similarly, Verizon CFO Matthew Ellis reiterated at the same conference the operator doesn’t expect 5G to have a significant impact on its financial results until at least 2020.

In addition to allowing time for use cases to develop and subscribers to sign on to new services, Stephens noted it could take up to five years for all of AT&T’s wireless customers to upgrade to 5G-capable devices given current upgrade rates. The first 5G smartphones are expected to be released in 2019.

AT&T has promised to roll out mobile 5G service in 12 cities via a Wi-Fi hotspot device by the end of 2018. Verizon launched a fixed wireless access 5G product in October and has said it plans to debut mobile 5G in early 2019.