I have 5 510 batt-box-type PTs, all purchased Sept and Oct. Two stopped working outright, even with fresh 10440 batts. Three work as PVs, that is their batts still power the atty, but they will not charge the batts from the USB. I have an external Li-batt charger now with a bunch of batteries. I keep them charged then swap them when the batt in the box runs low. If I open up the box completely I might be able to see why the power from the USB is not getting to the battery, but I've not done that yet.
The 510 PT is a very low cost device that is designed to give and take current almost continuously. Like most standard PV hardware, it is not meant to last forever...indeed the wiring and connections inside them are cheap and rather flimsy. A "straight-wire" 5V PT, one that doesn't have a batt box, should last longer, but this kind of device really needs to be on an external 5V power source, as it will draw while powering the atty more current than that which is required for charging a batt, and is more of a threat to USB ports, and possibly a mother board. But then I've read where 510 PTs with batt boxes fried mother boards too. Bottom line is PTs should be either plugged into an AC/5V-USB adapter (with at least a 1 Amp rating), or else a powered external USB hub.
All this said, the 510 PT for the money is a good investment, but since it costs about the same as a regular batt, and few dollars more then an atty, one should not expect their longevity to surpass those devices significantly. They are certainly not ultra-rugged high-end hardware, and their cost reflects that. And most vendors give a month warranty or more on their hardware. The chinese companies generally give up to 6 month warranties, but shipping is more $$ and slower, and you would have to pay to ship it back to china to exchange it.
However, since a well-built reliable chargeable PT for my 510 attys is very important to me, as soon as I get some money rather than buy another 510 PT I will be getting a Bartleby or some similar high-end mod.
but I'm a little 'challenged' when it comes to 'all things electronic'.. but I can be enlightened (as long as you use 'layman's' terms.... 
