We've renewed our annual service contract for 30 y...

We've renewed our annual service contract for 30 years, and both furnace and AC worked well with annual inspections and maintenance, so the recent diagnosis of a weak capacitor and $$ to locate the cause for a low coolant level (after spending $2k with them several years ago to replace the cooling coil) didn't seem credible given how well the unit is running this summer. I spent a nominal amount for a second inspection from a another long-time firm to confirm that both coolant level and capacitor are normal. Second opinions are prudent.