Does plugging iPhone into speakers shorten its life span? I yearn to play music on my external speakers that can be connected to iPhone or $50 USD 256 GB  USB flash drive. I'm assuming that both's life time will shorten. 


But which to use? I'm guessing USB, because it's cheaper to replace? 
Are there other better ways, without reducing lifespan of an electronic device? 


Rule out connecting to a laptop, which I don't always have with me.
Plugging a set of speakers into an iPhone does not significantly shorten its life span. Not at all.

If you're worried about the connector being damaged (for example a jack connector), you could use a permanently connected extension cable. Then you can connect and disconnect the speakers as you like without wear and tear on the iPhone's connector.