Out of trend as in not an IT bag anymore?
If I were you I'd keep the bags with classic shapes
For example: ysl muse is no longer an IT bag but the shape is classic so I'm keeping it ..etc..
A YSL Muse is exactly the bag I was thinking of when reflecting on this question! I have one as well, that I've continued to carry because of how special it was to me. Although I am so tempted to sell it, since I'm so limited in how many I can collect each year and would like to put the money towards my next one
@thisreallyreal, like others have said, it depends so much on what the bags are and your personal style. I would enjoy knowing what "out of trend" bags you are on the fence about! Many do come back or are reissued in later years, but if you don't want to take up valuable closet space (or the investment) waiting...