The only "mensajes de texto" I know are SMS, though the 50-year period is impossible (it's a factual error, not a grammar error)
I agree with ROBINDESBOIS that maybe the book isn't eager to accept the phrase as it is common but sounds the type you'd read in a headline or a sign. You may go:
Enviando mensajes de texto desde hace cincuenta años
that shows better the notion of continuity for a corporative ad, or
Llevamos cincuenta años enviando mensajes de texto
as "that is what we do" (Robin Williams will use a funny voice to add "Help us!")
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