So sorry to hear about your mother.
The answer is there is no reason to stop the steroids.
If she were not involved with a terminal disease then there would be cause to worry about long term effects.
the thing is, they are working because they decrease inflammation from the cancer and metastases
and this provides symptom relief
but there will come a time when they will stop working as they are now
and with her extensive disease there is no way to tell if she has one more month with you, a shorter time, or perhaps a few more months.
the steroids do nothing to stop the progression of the disease
and they do depress her already overwhelmed immune system
making it possible for her to contract a contagious disease like pneumonia
which would be very hard for her to overcome
so it is possilbe that the cancer will ultimately cause her death
or that an infection or bleed in the brain will do it
I'm so sorry
I wish I could give you better news and a better time frame for your expecations
But I simply cannot
are you there ma'am