In the past I bought four third party batteries (a pair of
Wasabi Power first, and a pair of
DOT-01 after Wasabi failed) and they degraded much faster than Pentax D-LI 68 which is still going OK after about 33 months.
After all, I don't expect that a product that costs me 1/6 to 1/7 of the OEM per piece works as well as the OEM, that's OK, but I'm curious to know your anecdote. Here's mine.
I've gone through a pair of Wasabi batteries in just 17 months.
They were OK at first, started losing the capacity after some months (maybe 6 months?), and finally started to swell/bulge to the point where it was hard to remove from the camera, so I stopped using them.
I've bought a pair of DOT-01 batteries after Wasabis failed.
Just like Wasabi, they started losing capacity after some months. Now after 14 months, they still work but my 33 months old Pentax gives me 1.3-1.5 times more shots per charge.
I strictly rotate between my batteries, e.g. Pentax, Wasabi 1, Wasabi 2, Pentax, Wasabi 1, Wasabi 2....