I've a similar experience living in a humid climate. My patent lady dior developed that stickiness after 6ish years or so (I also had this problem with patent shoes). Even if the stickiness isn't that obvious to the touch, dust starts getting stuck to the surface making it look dirty. My patent lady dior also then started to crack and peel after around 10 years. This is notwithstanding that it was stored in a cool dark closet with moisture absorbers and in a room where the air conditioning is turned on every night. I've stopped buying anything patent no matter how appealing the item might be.
On the other hand, my lambskin lady diors have held up very well so far - I would suggest going with lambskin instead of patent.