Long-term engine reliability is a matter of several factors, of which basic design is only one. Assuming an engine is sufficiently lubricated both in its design and how it is maintained, theoretically there is no reason why a downsized turbocharged engine should suffer more wear than larger naturally aspirated engine. As for maintenance costs, this again will depend on the specific design of the engine rather than its layout, although it is worth considering that a smaller turbocharged engine is likely to be considerably more efficient than a large naturally aspirated engine and will therefore cost less to fuel, which is the key benefit of this approach. Long-term performance also tends to be mostly influenced by how well an engine is maintained. A turbocharged engine has additional components compared to a naturally aspirated engine so in this respect there is more that can fail. Ultimately the more simple an engine is, the less there is to go wrong and therefore theoretically the greater potential longevity it has, but at the same time the less sophisticated an engine is, the lower its specific output per litre will be, and its capacity would need to be increased to match the performance of a smaller, more complex unit.