Long term reliability and maintenance cost of Hyundai Venue CNG?

With the introduction of factory fitted CNG kits in vehicles like Hyundai Venue, a question arises about their long term reliability and maintenance cost. Though CNG vehicles are known for their low fuel costs, there are questions about the durability of CNG specific components and how they will impact the life of the vehicle as a whole. While some are concerned that the CNG kit will present problems, will put more strain on engine components, or require more servicing. Yet others believe that factory fitted CNG systems are more reliable than aftermarket installations and that the savings in fuel costs are more than the additional maintenance costs. The comparison often gets extended to discuss the total cost of ownership (TCO) between CNG and petrol variants over a period of years the resale value, part replacement cost, availability of technical expertise to serve the CNG system etc. A question that this question also raises is the broader question of owning a CNG vehicle and associated experience over the period of ownership and financial planning.