What you're missing out in calcium, fluoride and other minerals in distilled water can be more than made up for with a healthy diet. I disagree that the minuscule amounts of additives you consume from tap water can make you any healthier.

If you have high TDS and low water pressure, there are RO units out there that are specially designed to address these issues. I imagine a 3 stage pre-filter, booster pump and a decent RO unit will be able to last several years if well maintained. I only have ~330ppm TDS and decent water pressure so I run a basic RO unit that's still producing <10ppm TDS water after 3 years of service with only basic pre-filter changes. Check out the spectrapure line - they are more expensive than the ebay no-name brand units but they are very extremely well built.