How long should a "jet trail" linger? A few minutes or all day?
Depends on a lot of variables, they may not form at all or they may persist for hours or days, or they may seed cloud formations that last even longer. Temperature, relative humidity, altitude, the level of particulates, how well tuned the plane's engines are, will all play a role. The trails are formed by water vapour in the exhaust condensing and freezing, so they need condensation nuclei (i.e. dust particles), if the relative humidity is very low they'll disappear almost immediately, if the air is near saturation they'll persist for a long time, and so on.
Vander Zalm strikes me as the kind of whack job who'd worry about chemtrails, but I've seen no confirmation or denial that he wrote to anyone about them. Chemtrails seem like pretty much a damnfool idea to me, if anybody wanted to expose us all to certain chemicals there are far easier and more controllable ways to do it than spraying stuff into the atmosphere at 25,000+ feet. Food processing and water treatment are the obvious targets.