The key to writing stand up comedy appears to be drawing upon an issue or event in your immediate life with links to the past, conflicting values, or interests and almost reporting on it, but doing so in a very quirky way. I've found some YouTube videos of stand up comedians I have often laughed at to demonstrate this... Here's one from Fiona O'Laughlin...
Here's a fairly gentle set in terms of mid life changes from Mario Joyner on Ageing Gracefully ...
Here is a set from older female perspective from Karen Mills on "Aging - You've Got to Find the Humour."
Here's a more X rated/devastating one from Billy Connolly on Prostate Examinations.
Do you remember Dave Allen? Here's a classic from the late Dave Allen on retirement and aging...
And here are some handouts on writing standup...
Writing Standup (Guardian article)
Comedian's Toolkit (Guardian article)
Writing Comedy Sketches That Work
.... and for further reading, if you want to perform to a crowd and avoid common errors, try Part 1 and Part 2 of 'How not to suck at writing stand up comedy'.
BL