I wouldn't worry about that. Typical NAND flash has 100k+ write cycles
I'm sure iOS has a smart file operating system which distributes writes evenly to reduce wearing out specific locations.
I'm also sure that once it starts happening with some sectors it marks them as bad ones and relocates them to healthy locations as it happens with normal HDDs as well.
Also writing on the same location in every 30 sec is not particularly frequent. It would take you 140 years to wear out the same flash location.
I is likely that most of your data stays in the cache without actually ever written to the flash.
