Why the lifespan of Giftia is only 10 years? I was wondering why the lifespan of Giftia is only 10 years, is there any specific reason for that? Something happens to their OS or what when their lifespan is complete?
According to the Plastic Memories wikia the Giftias' programming becomes corrupt as it fails to overwrite old information after 81,920 hours of service.

There aren't any specifics for why this happens, but from an IT viewpoint this could happen either because the data storage in Giftias are designed to work for this long and it starts to break down (in today's terms, the drive starts to have bad sectors), or the storage can only be written once while the data fills it up at a steady pace over 81,920 hours, and after it's full the OS makes attempts at overwiting old data which isn't possible, but this process might the old data or even the storage itself. But of course, this is just guesswork.