You uh, can also get stacks of ventures from Boarskin and Piesteskin treasure maps.

I gather up a map every day and do the Ixali quests everyday. The only reason my ventures have started decreasing is because I've been sending my to i82 retainers on quick ventures in order to get the new dyes. Though Normally I hover around 70-80+ ventures in my inventory, moreso when I get a chunk from maps.

Ventures are super easy to obtain and with little effort.