I switch bags daily so they all get used eventually, just not at the same rate. Some of my bags are used more in the summer so they get more sun exposure and the vachetta darkens faster. Others, I might decide I want to use for a week at a time (ex. my Batignolles Horizontal) and that darkens them faster as well. I'm not really concerned with the vachetta color as long as it's not TOO dark (my mom's vintage bags don't count) and if I buy the bag from a reseller (I've only bought one from someone else-the peach graffiti pochette), I don't want the straps too dark because I want to be the one who puts the most patina on them. Otherwise, I don't really mind. My mom's taken her black MC speedy out in the rain and I've done the same with my white MC Alma and it didn't bother the patina at all. If anything, it evened it out.