In January 1917, Lenin thought the revolution would not happen in his lifetime. Conditions were very different then, but it's a good reminder that life is unpredictable.

We of the older generation may not live to see the decisive battles of this coming revolution. But I can, I believe, express the confident hope that the youth which is working so splendidly in the socialist movement of Switzerland, and of the whole world, will be fortunate enough not only to fight, but also to win, in the coming proletarian revolution.

https://www.marxists.org/archive/lenin/works/1917/jan/09.htm