No, it does not have any impact. In fact, your SanDisk memory stick has a very generous warranty: a lifetime warranty. According to this (already outdated) article, modern durable memory has a "write endurance" of anywhere between 100,000 and 1,000,000 cycles. So, realistically, even if you manage to write to your card twice every day, it will last between 100 and 1000 years. It's no wonder you get a warranty like this.
So if you manage to live that long or manage to get that many I/O operations out of it and kill it: fear not. You can just get a new one.
That said, I'm unsure about fragmentation on devices such as these. If you regularly fill the stick to (near) full capacity, data could fragment fairly quickly. A regular formatting or disk defragmentation will resolve this, and has no ill effects on the stick. I stand corrected that defragmenting memory cards is indeed bad practice. If you run a defrag long enough, you might actually reach that write cycle limit. Just don't do it since it has no added performance benefit.