Changing brand after many years with the same one
Short answer: Buy one piece first and wear it for a month. Never replace the whole drawer at once, however good the new one looks.
Why you should try first
After many years with the same brand your body knows the exact fit. A new brand can have the same size on paper and still sit completely differently. You only discover that after a full day of wear.
What to measure
Chest width, hip width and length on the garment you are happy with. Compare with the new brand's table in centimetres. See bamboo underwear for men.
When a change makes sense
When your old brand has changed its cut, when the range has been discontinued, or when you want a different fabric. See JBS of Denmark and Bamboo Basics.
Frequently asked questions
How long should you test
A month of ordinary wear and a couple of washes.
What if it does not fit
Then you know after one piece rather than after ten.
Can you have two brands at once
Yes. Many people use one for everyday and another for training.