Same experience as many here for me when leaving two companies with a quite long but somehow standard 3 month notice here in France: it felt nice to give my managers/coworkers some time, but overall it wasn't useful. Most of the 2 first months was "as usual" and the real information sharing was done somewhere during the last month. The last week or two were absolutely useless for me and others, as it's just wandering around without any precise task, and everyone being like "oh, you're still here?"