I use XPSs for home and work, and my understanding is that they don't implement one of the sleep state capabilities properly in hardware so full "deep sleep" , next to zero battery mode isn't possible.
That said, my XPS 13 will suspend for a couple of weeks on battery once it's configured, even given this caveat. I haven't shut it down when I finish using it since I bought it in 2019. I run Ubuntu LTSs.