I have had 2 smc batteries. The first was replaced under warranty.
The second which is less than a year old has "puffed" about 3 mm in a hard roar case.
SMC is going to discount a replacement battery for me.
If its not a really "big" discount, then I too with go with Thunderpower.
I have had other batteries puff, but that was after 18 months, not 6-8 months.
I have a Maxamps I got the same time as the SMC and it is still working great, no puffing at all.
At time point I would recommend going with batteries from Thunder power or Maxamps.