Shortening prayers when travelling somewhere one will stay for more than 15 days

My husband and i travel very frequently for his work. so far i understand that if we travel beyond 77km for less than 15days we are required to pray kasr prayer. however, if we KNOW that we will be in a destination further than 77km and for longer than 15 days (before weleave home) do we pray standard prayers (non-kasr) from the day we reach our travel destination, OR do we pray kasr prayers for the first 15 days then switch to standard?
wasalam

Walaikum assalam wa rahmatullah,

I pray this finds you in the best of health and spirits.

When travelling somewhere one will stay for more than 15 days, it is necessary (wajib) to shorten during one's journey until one reaches the city limits of one's destination. In such a case, one would be considered a resident at one's destination and would not shorten prayers--rather, one would pray them in full, as a resident must. [Ibn Abidin, Radd al-Muhtar]

And Allah alone gives success.

Faraz Rabbani