You are right...it is not slow charging that results in puffing. As wildthing said above. Is it worth getting a decent charger? Absolutely....that way you can monitor the voltage of each cell as it is being charged. You can tell quickly if a pack has issues if you see widely variable cell voltages...and a good charger will try to balance that out while charging. I've owned a bunch of the affordable chargers.....the $40 all-in-ones. And they do a decent job. But once I got quality packs I decided to invest in a quality charger. I bought a HiTec charger...forget the model but it was about $80. And while it offers only a few more features than the cheaper chargers...it seems to balance the packs better...keeps them healthier...and will do 10 amps if I do a 12v source. It's kept my expensive packs going for a long time.
By t I also have a rack of very slow chargers...the ones that come with sown of the airplanes you can buy. From time to time I'll throw packs on them to start the charging process...or just bring them up to full voltage slowly. It's just a time thing for me.
I have seen those HiTech chargers you referenced and you could hear me scream all the way from TEXAS if I had to spring for the bread to acquire one of those!!!ha! chas