This positive resignation letter can be used for older employees who are retiring from the company.
After (XX) years of service to (the company), the time has come for me to retire. Please consider this letter formal notice of my intent to retire effective (date).
I hope that by giving notice relatively early that I will be able to assist in any necessary training and make this as smooth a transition as possible. Additionally, please don't hesitate to contact me after my retirement if you have any questions about (specialized knowledge).
My time with (the company) has been a pleasant, fulfilling experience. While I will surely enjoy the leisure time and intellectual pursuits afforded by retirement, I am sad to leave and will miss my colleagues, many of whom have become true friends.