Sometimes I still make mistakes with size, so a friendly exchange policy is very helpful. A simple pair of glasses or a basic jacket that always works is worth a lot. Smaller shops can be surprisingly friendly if they care about repeat customers.
If anyone is interested in real user experiences, I sometimes write short notes about the shops I test.
You can find one of the pages here:
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Of course shipping delays can happen, but good communication reduces stress. Whenever I find something that actually works well, I tend to reorder it later. In the end it is all about finding what matches your own habits and lifestyle. It makes it easier to compare with an old pair of glasses that already fits well.
Just sharing my personal feedback.