It can take 6-12 months for implants to feel like they are part of you. Some patients may feel their implant longer for different reasons (capsular contracture, very thin breast tissue, implants that displace a lot when the chest muscle is flexed due to a stretched out capsule). The larger your implants, the more likely you may encounter some of these problems.
Silicone implants have less rippling than saline implants. Also grafts like Alloderm or Strattice (as well as many other brands) can help support the implant and thicken the soft tissue coverage to minimize rippling.