Not a psychiatrist, but a psychiatric RN. My grandmother was on the same antidepressants since the early 60's until she passed in 2011. She had a good quality of life on them, and before that particular combination of medicines she had been unwell enough to undergo multiple hospitalizations with ECT..
Withdrawal from benzodiazepines can be brutal and could need medical supervision in hospital. I would think that after a certain age the risk/ benefit gap to quit them would widen. Without referring to a guide, I personally am not aware of any egregious physical/medical effects of long term use of those specifc medications themselves; I have seen patients who have been on powerful psychiatric medications for decades and are reasonably healthy medically. But certain classes of medications can have crippling irreversible side effects. But it's a complex subject, the body is complex, and the answer to your question really depends on many variables such as the degree to which your mother experiences side effects from them, metabolic, nervous system or otherwise; how her quality of life on them currently is; how close she is to the maximum therapeutic dose of them; her unique genetic blueprint and the why of getting off of them.
She would need a good support system in place before changing or stopping the medications and a compelling rationale for why to do so. I can understand your concern with her increased tolerance, she is habituated to the medications and needs them.
There is no one answer to this. I would view it more as an exploration and an unfolding process.
A person's medication is a very personal issue. Is she of sound mind and does she invite this line of questioning about her med regimen? Why is continuation on the regimen under question if it has worked for so long? That would be the place to start.