No issues at all, black patent held up better for me than any other material. Don’t own my black patent mini anymore but other than carefully checking how the leather behaves during storage, I did not take any special care
I have a black patent ML classic flap for 9-10 years and no issues. I can bravely wear it in the rain and no colour transfer so far. I do find I have to wear more dressy clothes with it and that's the only downfall.
I have one black patent Chanel bag from 2012ish, I can I honestly say that not only is it very well made and absolutely beautiful, but out of all my Chanel bags (including 5 CF's), it is THE ONLY ONE which retains that beautiful, brand-new leather scent to this day!!! It is a joy to take it out of it's dust bag and use it. Also, the quilts are as puffy as the day I brought it home! Post pics if you get it!
I love black patent and it holds up very well compared to lambskin. As long as you choose black or a dark patent color, you will not experience the yellowing or discolouration on light coloured patent.
I think if you own patent, you fully understand that storage and temperature control is crucial. If you live in a tropical climate with no a/c, it will be an issue. However, if your home is climate controlled, there should be absolutely no issues. I love wearing patent during Xmas, it is something different from caviar and lambskin and that slight sparkle and gloss look makes it look festive. I like wearing patent in the summer too but you have to be careful not to leave the bag in the car. Patent bags that are for sale are usually in fair condition and have not been properly stored and the owner did not fully understand what it meant to own patent. Hence, the low resale value. Hth.