Fresh anti-freeze is a good thing. Some people measure it's specific gravity with a hydrometer; then they assume it's good. They don't realize it's not the freeze point that matters. It's the anti-corrosion package that gets used up and you can't measure that by specific gravity.

It's always good to FIND the source of a leak. THEN you can decide if it's worthwhile to fix it. It might be something as easy as replacing your oil-pressure switch (which are known to leak).