In research on verbal periphrases, analyzability constitutes a central parameter, both for describing the grammaticalization processes to which these constructions are subject and for defining their categorical status. This paper focuses on a specific verbal periphrasis: [tardar en + infinitive]. Its historical development is examined, along with the recent emergence of a dative of interest in this construction, drawing on quantitative data from various digital corpora. The findings show that over time en became the predominant linking element between the auxiliary and the infinitive and that the order of the components of the periphrasis gradually became fixed. The data also reveal that the new pattern with the dative of interest occurs more frequently in informal written language and colloquial registers, where the object pronoun contributes to clarifying the construction’s potentially opaque meaning. We argue that grammaticalization has reduced the syntactic analyzability of the construction, whereas the incorporation of the dative of interest points to speakers’ perception of tardar as an independent verb, thereby reflecting increased analyzability. This case study illustrates that the analyzability of a construction is not necessarily unidirectional, but may fluctuate over time, shifting in different directions at distinct historical stages.