I have a few old Contax IIIa cases that are in pretty good shape. The leather is getting stiff so I need to treat it with something before the front starts to split from the bottom. What could be used to keep the leather from ripping?
Personally, I treat mine like I do a good pair of shoes - I polish them. If you use shoe polish in the same tones as the leather on your camera or case, then you also bring it back to life looking like new.
The best thing for dried out leather is neatsfoot oil. This will restore the leather's flexibility. Apply the oil sparingly allow it to soak in and then wipe to remove any excess. Several treatments may be needed in the worst cases. To clean leather use saddle soap.
Neetsfoot oil is easy to over do. You can use Lanolin cream which is natural and has no harmful solvents. You can find it in the grocery store or pharmacy as "nipple cream" for breast feeding mothers. Pecards is a cleaner and dressing for leather and works very well, even on antique leathers.
I've used both with good results on some items in my antique collection, especially dry and cracking leather.
I use a product called Flexalan (available on Amazon and at saddle and horse shops), which is a mix of neatsfoot oil and lanolin. The lanolin helps the most. Like Xander said, neatsfoot oil is easy to overdo, so be careful not to apply too much.
Huberd's Shoe Grease. Works great on cameras and boots. I use it for almost everything involving leather. As a bonus you can run it through your hair when you're done.
You can get an oil version as well but I much prefer the grease.