Not very often;
My light has been hanging on my belt for 9 years, the SAK 13 years. Did replace the belt sheath, worn those out...

Watch is a Frankenstein of parts from the same model of watch I bought three times and replaced bits and pieces of them to get a working one. First one was bought 11 years ago.

Wallet does need replacing, have some repairs on it and still have some extra pockets it shouldn't have. I hate shopping for a new one...

Replaced phone almost 16 months ago, after the previous one really started to be an issue after 5.5 years of service with 2 worn out belt sheaths and a replacement battery.

Might need to replace the patch kit for a bike (ride my bike to work, supermarket, etc). Haven't used it since I upgrade to puncture resistant tires.

Pens, tissues, plasters, etc. Those things just get used/lost and replaced.