The short answer: It varies, but more likely than not, a long time.
Take for instance an operation finally shut down last month involving drug traffickers with Mexican cartel ties. The Star Telegram reported that federal, state, and local authorities investigated nearly five years before finally moving in on a ring distributing narcotics in North Texas.
Thirteen suspects were arrested after FBI agents raided a home just across the street from an elementary school in Grand Prairie and seized 380 grams of heroin, five kilograms of meth, and a shotgun. In conjunction with the same investigation, seven weapons and cocaine were being discovered and seized from two other locations in Dallas at the same time.
If the suspects are convicted, [...]