I got no idea how accurate this info will be, but my experience is, I had my panel on the roof for well over a year before I connected it to a controller to charge the batteries.
Got around to start setting it up, then basically got lazy, and only had a cheapo PWM controller and two 200ah batteries. Couldn't find the ideal(ie. long term) spot to mount the cheapo controller, etc ... so got forgotten .. and then lazy.
Finally remembered, a year or so later, to get myself the controller(in my case Victron) and some cables and connectors and so forth and connected it all up.
Panel is cheapo, but still can give me up to 100W in ideal conditions.

