I took it for two and a half months.
Since it is so commonly available in India, I purchased it from a local whole-seller who is into selling pure ayurvedic herbs. The pack has no famous company name attached to it, but I know this guy is supplying to other retail stores who then sell it in their name.
Triphala–if pure, ideally is so effective that within three days you should see substantial difference. Maybe you can try the capsules, and if you don’t see any improvement you may opt for for powder next time, or vice versa. Though I would go for the powder, as it is less expensive here.