If you know the equipment isn't going to last 39 years, do you have the option to depreciate it for a lesser amount of time?

Ive got a client replacing the roof and HVAC ducting on a commercial building this year.  The last time he did it was back in 2005, so the equipt lasted 15 years.  (this was my ex-employers client and he set it for a 15 year depreciation back in 2005...how he knew it would only last that long, I have no clue)

Do I really have to depreciate this new equipt over 39 years when in all likelihood this will only last 15 years as well?