The 2007 Nissan Service & Maintenance Guide
recommends changing the inverter coolant at 60,000 miles (as the OP noted) or 48 months.
I have attached a copy of a "Nissan & Infinity Tech News Feature" article on "Altima Hybrid Service", which may be helpful. On this topic, it says:
Coolant should be replaced for the first time at 60,000 miles or four years from the production date, whichever comes first. However, after the first coolant service, the coolant replacement interval is shortened to every 30,000 miles or two years. The Altima Hybrid has two separate cooling systems: one for the ICE and one for the inverter and transaxle. It is important to read the service manual procedures before attempting to replace coolant. Improper procedures can lead to damage.
The Altima Hybrid uses Nissan Long Life Antifreeze for both the ICE cooling system and the inverter cooling system.
The article also includes some tips and photos.
The OP's mechanic's friend's advice sounds bad to me. I would try to find someone who is willing to follow the manufacturer's recommendations.