That being so, I’m fine with “ances” so long as discrete plural things are intended and there is sufficient precedence. So “resonances” meaning discrete, measured instances of resonance works for me, but I’d be leery of using “insurances” for insurance policies. Two Reliances would be fine, if you were referring to something like Reliance buses, but I would avoid using two “reliances” for my reliance on two different people.

Ultimately, it comes down to what usage you feel comfortable with (or you think you can get away with) because enough people have used it before you.