Can people re-use my patented products once I sell them?
Yes they can. In the case of Calidad Pty Ltd v Seiko Epson Corporation  HCA 41 the majority of the High Court of Australia ruled that the first sale of a patented product exhausts the patentee’s exclusive rights in that product.
Seiko makes Epson-branded printers and ink cartridges. The High Court determined that patents over Epson brand printer cartridges made by Seiko were not infringed by Calidad Pty Ltd who sold re-filled ink cartridges with reprogrammed control chips.
Seiko’s patents claim a layout of electrical terminals that reduces the risk of shorting between the high-voltage supply for the sensors to monitor the ink level and the low-voltage supply to operate the memory chip.
The High ruled that the patents were not infringed because the patentee's rights of use with respect to the particular product do not survive its sale. The purchaser of a patented product buys “’the use of the whole’ of the combination”, as would result from an ordinary sale. The patentees rights are exhausted when the reward which is the object of those special rights is achieved by the patentee. The sale takes the product outside the scope of the patentee's monopoly rights.