[Samsung Galaxy Exhibit 4G] cmikeh2:
The Short Story:

Flash storage like this will generally have at a minimum 3000 write cycles. Furthermore, reflashes, despite the same file location as the prior files, do not necessarily occur in the same physical location due to software controllers (at least on desktop SSDs) that are designed to promote longevity of the device. In the extremely unlikely case you do exhaust the write cycles, the data would be read only for a period before it is rendered unusable.

The Long Story:

Disclaimer: I have no idea if the memory in our phone is mounted flash memory or an internally mounted microSD card.

The Structure of Flash Memory: Flash memory is composed of a series of blocks of floating-gate transistors (cells) that can each store information by storing a specific electrical charge. The most expensive type of solid state drives are Single Level Cell drives, in which each cell can store either a 1 or 0 based on the charge. Since each cell stores two states, the margin between each charge is greater and the degradation of the cell that occurs through writes (to be discussed later) creates less "software" confusion in reading the data. However, the higher cost of SLC drives has led to the mass production of Multi-Level Cell drives (MLC) which generally store two bits of information (00, 01, 10, 11). However, structurally these cells are only marginally different from Single Level Cells and therefore have smaller margins of error. For a complete product, blocks of transistors are scaled into larger units (whose name I can't remember) and then paired with an interface to exchange data with the rest of the system.

The Read/Write Process: Unlike magnetic memory, flash memory cannot actually be overwritten and must be wiped before any new data can be stored in the specific cell. Furthermore, flash memory itself cannot erase the data in a single cell and must wipe the entire block of cells to write new data, resulting in slower data transfer speeds. While this poses little problems on larger capacities, the minuscule amount of memory in our devices means that we inevitably will encounter this process a number of times, especially as the devices grow older. To explain this, imagine a five cell block of information. In the first three cells, we store 01, 01, and 01 (since I am fairly certain our devices contain MLC flash). Later we write a 10 in the fourth cell and shortly thereafter tell the OS to delete the 10. To the OS, the fourth cell is now open, but to the storage device controller, there is data in the fourth cell. Later, we decide we want to write 0101. To write this data, the flash memory controller copies the data into a cache before clearing the entire block of data. Finally, the controller writes 01, 01, 01, 01, 01 into the five cells. AS you can see, the process for writing once cells become filled takes an increasingly long time while increasing the wear on the cells.

Cell Degradation: When a floating-gate transistor is given a specific charge, the silicon of the transistor slowly deteriorates. While most MLC flash has a write cycle lifetime of between 3,000 to 5,000 cycles, SLC generally has double or triple of that value. This occurs due to the smaller margins of error between the charges in each cell. To explain, imagine a cell can accept a charge of between 0 and 12. In SLC, a charge of 0 would correspond with a 0 and a charge of 12 would correspond with a 1. However, in MLC a 0 would correspond with 00, 4 with 01, 8 with 10, and 12 with 11. As time progresses, the accuracy of a charged transistor decreases. After 3,000 writes, for example, a transistor may read a 2 when in reality it is a 0. For SLC this make little difference because a 2 obviously corresponds to the 0 and not the 12. However, in MLC, 2 is directly between the 0 and the 4, rendering the data incomprehensible to the OS. The controllers for the flash memory can normally detect when a cell will soon become effectively useless and define the cell as read-only, which has a far smaller effect on the durability of the transistor and allows the data to survive as read-only.

Conclusion: With cell phones, the problems of read-write cycles will probably not effect basic usage outside of speed. A study done by AnandTech concluded that by writing 10 GB of data (with a 10x amplification factor) for a total of 100 GB of writing per day on a 100 GB SSD would result in a lifetime of 8.3 years. With the rapid evolution of the smartphone market, it is unlikely that you will use your phone while writing to full capacity every single day for 8 years.

The Links included are not links to any additional information except for the "study" conducted by AnandTech. The others are shopping links that XDA appeared to have inserted for me.